This is a great question. Thanks for everyone's feedback. You know, I'm pretty sure that 5S162 (around Jan. '65-San Jose) had the metal ones. I know I put metal ones back in it when it was restored, but that was over 20 years ago.
Brant: That time period at San Jose is one I've been extensively studying the past couple of years. I have found nothing but plastic door jamb switches used then.
The tab fits into a notch molded into the side of original style Autolite batteries. The tab was most likely removed so that the clamp would be compatible with after market batteries.
Unfortunately we currently have no production data for 65-66 cars. It is possible, though, that the previous owner may have queried Ford for statistics in the 70's and might have gotten a reply. I have heard there were a handful of stats provided to people that inquired before the data was destroyed.
My body man is supposed to be putting together a black "color wheel" for me with varying shades of black. I can then use this to compare original parts as they are cleaned to try and get an idea of what would be a close replication. As Jeff says, nothing is really definite, but we do see patterns after observing original cars. For instance, we know the engine bay braces on '65 convertibles were painted with black lacquer paint which isn't very resilient! Something else to consider is that Ford rarely, if ever, used primer on parts. Instead they were usually zinc plated or left bare metal before paint. This could also have an effect on the final surface texture and gloss of painted parts.
It appears the MCA rules need to be revised.
Until we can find more evidence, you are correct that the rules ought to be revised to allow either one. There have been a lot of 65 and 66 Unrestored cars found with the "tang" version clamps, so the drawing may not be as clear cut as Jeff indicated. I know you're probably tired of me saying it, but if we can find a blueprint for the clamp, it might give us more accurate information.
The Ford document provides support that Ford manufactured clamps with & without a locating tab/tang.
Yes, there is no doubt about that. The question I posed was whether or not the 9/64 drawing that you referred to was moving from the very early style clamp to the one we commonly see with the tang. I have seen many examples of cars built way past the 9/64 date with a tang 24F hold-down.
One on the right has the tang, the other doesn't. I think the original intent of that image was to show that even though there was a change, the p/n remained the same.
The Ford drawing provides support for both clamps.
Not sure I follow what you're saying here. The image of the drawing I provided shows a clamp type different than either of the ones you provided in the pic.
Quote from RalphJrBoth my April '65 K and Sept '66 A have the metal ring / black button switches.
Yes, but what assembly plant? Typically in '65, Dearborn/Metuchen used the metal ones and SJ used the plastic ones.
Check AMK p/n F-347...
I've seen an "early" tang version which just has a tab sticking out on the end. The style shown in this drawing: http://www.early-mustang.com/charles/hold-down.jpg
Could it be that the referenced 9-4-64 engineering change went from this earlier version to the more common "down-turned" tang?
I have an original door that I can try to get a template from. The door is at my body man's shop though, which is about an hour away.
Cool, appreciate the effort Mark!
Once you figure out how to make the tang, would you consider taking some NOS Ford ones w/out the tang and modifying them?
Also, not sure that you should consider doing the 22F size as there is no correct battery being reproduced that the tang would fit into. All of the NOS size 22F clamps I have ever seen had the tang too.
Yep... hipoHerb
Soooo you plan to be done in about a month right
I have 2 months before the MCA national here in Raleigh 
I'll be updating the blog nearly every day from now until the car is finished. For those interested in keeping up, you can subscribe to the blog and get notifications when it's updated. Or, just check it once a day.
Quote from J_SpeegleAs far as fit - I can't believe how well many of the the original cars fit together - wish some of my new car's body panels were that well aligned
Agree with Jeff. On the last few cars I have done with all original sheet metal, the fit has been very nice. The K convertible going together now has amazing door to quarter lines.
I need to get that old rear assy. out from under it and take more pics of the undercarriage. There's lots of detail under there!
Updated the blog:
More pics:
http://www.early-mustang.com/charles/K_vert/4_27_09/
After going back through the pics, I did find a touch of body color over spray at the firewall on the wheel well side. Nate will be happy to see a little here:
http://www.early-mustang.com/charles/K_vert…27_09%20004.jpg
(I had to re-paint the engine bay, so black is over the top of the burgundy over spray)
Will be updating the blog pretty much daily from here on out.
I notice that the one in the picture is installed vertically and mine was installed horizontally- does it matter? or is it possibly assembly plant specific?
It varied from car to car but was typically in the horizontal position. I only deviate from horizontal if I know the original orientation of the one on the car I'm restoring... and have a pic to back it up!
