[BruceWilkie]

Gavin thanks for bringing this back up. I've had little time myself...then it got HOT and muggy.

I made a slightly different starter adapter plate for my early starter. (Temporarily its aluminum but was easy to work with home shop equipment)

Anyway the starter(using the early starter) and its adapter can be removed as an ASSEMBLY then starter can be removed from starter adapter plate.(removing or modifying transmission NOT required). Tested both BOP and chev T400's

My starter bolts are countersunk allen bolting thru starter adapter plate holes .

Securing starter and its adapter to the engine adapter plate....the upper fastener is a stud in 61-64 big car starter hole on engine adapter plate (faces front of engine)and requires a 7/16 thread 12 point nut (1/2" box wrench) for comfortable working clearance.

(Fwiw the contact area is the same as an 11/16" 8 point nut which makes wrenching slow and challenging)

A 7/16 stud on starter adapter (facing transmission) comes thru the lower 61-64 big car starter hole on the engine adapter. I used a 12 point nut there as well so you can use the same wrench you used on upper nut(12 point 1/2" box wrench).

The modern flex plate cover needs trimming to clear differences but will otherwise bolt on.

61-64 big car starter came in two varieties. The common solenoid high version has a threaded hole in upper position, you'd need a hole in trans to access it. The less common "upside down" or "421 starter" will bolt on. I've seen the upside down starters on 2 64 389 Bonnevilles so it wasn't exclusive to 421.

Delco only offers the solenoid high as a reman. 55-60 starters are easier to find at part stores.

BEST starter option IMO is the IMI 61-64 big car mini starter(Butler). RARE also offers a mini for 61-64 and it offers more clocking options.

Headers(common apps) may need some mods to avoid starter interference or just too close to solenoid (heat concerns). The mini starters should resolve that.

My 58 starter and adapter clears the kick-out on my Canton pan but header tube(old 3 tube) touches solenoid.

I'll post pics later.