I believe your 10" clutch pressure plate is a Laycock diaphragm unit as fitted to earlier 4.2’s - the 3.8’s had the 10" coil spring style pressure plate and later 4.2’s got the 9.5" diaphragm clutch (depending on build date). Have a look at this thread for some background info + a bit more on the subject - it includes a good summary by @davidxk regarding clutch fitment by model. Suggest you check your flywheel to see if it’s drilled for both 10" and 9.5" clutches:
Have a read: Clutch: replacement problem
IF you have the correct flywheel for a '67, it WILL be drilled for a 9.5" clutch. It MAY be drilled for a 10" as well. In any case, if you do NOT have the correct holes for the clutch you want to use, take the flywheel and new clutch to any machine shop, and they can easily, and inexpensively, drill it to fit the new clutch.
Do you believe there have never been poorly manufactured spring clutches??? As a matter of fact, I know several people on this forum who have installed defective spring clutches in just the last few years. So, not sure what point your’e making. If you buy a defective product, it will likely fail prematurely. Buy a good quality product, and it likely won’t. I stand by my statement. A diaphragm clutch is always the better choice. And don’t buy defective parts.
Mine '62 came to me with a spring clutch and whilst it was all apart I had the flywheel machined and drilled for a 9 1/2" spring type clutch. I find the new clutch more progressive than the old spring 10" - which itself was a low mileage unit when I pulled it out.
Yes, I was generalizing a bit there. For clarification, this is all summed up rather well in @davidxk’s post as I linked to above. Here’s what he says in fuller details for those who may not have read it.
[quote=“davidxk, post:6, topic:390959”] This thread may benefit from a little clarification (or confusion if I get it wrong ) concerning the clutches fitted to E-Types.
The first 3.8L E-Types were fitted with a 10" Borg&Beck Coil Spring Clutch Pressure Plate. In Feb 1964 (i.e. still 3.8L cars), production switched to a 10" Laycock Diaphragm Spring Clutch Pressure Plate. The 10" Laycock Diaphragm Clutch continued well into the 4.2L cars. In June 1967 production switched to a 9-1/2" Borg&Beck Diaphragm Spring Clutch Pressure Plate.
So, the original poster’s 10" Laycock Diaphragm Spring clutch was standard fitment to his March 1965 car. Nothing odd about it at all. The 9.5" clutched weren’t introduced for 2 more years. [/quote]
In that post from May 2020 David mentions the 10" Laycock diaphragm clutch is “no longer available” so the choice for the OP is either a 10" coil spring clutch or the 9.5" diaphragm clutch - the latter is what the factory used from mid-1967 until the end of E-Type production although the Series III V12 has a 10.5" diaphragm unit. Good luck with your project, Hal.
And one important point to mention in this context: Every clutch pressure plate had a different carbon throwout bearing (TOB) to account for the different height (flywheel surface to pressure plate pad for the TOB) of the pressure plate. You CANNOT mix and match them. You need a matched set of Pressure Plate, Driven Plate, and Throwout Bearing.
I think the last time I was looking for a 9-1/2 inch clutch cover I found a 1960-70 six cylinder Ford application that used one?
I am blessed with a local clutch rebuilder that can put together a disc and pressure plate for virtually any combination to virtually any specification. The long-time owner, who recently passed away, was one of the better oval track drivers of the 1960-70’s.