Just to chip in my 2d's worth (or should that be 2cent's worth
), I can add a bit about the thicknesses from the Brian Buckland manual on rebuilding an Elan. He shows lots of engine block identification marks and comments that the stamping on the left front face should be LAA, LA or LB, and as you say it's related to casting thickness. He says the LAA was the thickest and hence most suitable for large bores, with LB being the thinnest.
He also has pictures of a cast "L" between the 4 holes where the engine mount goes and says that although cast by Ford this denotes a block made primarily for Lotus & Ford Twin Cam engines. He splits the blocks into 3 categories;
1 early Mk2 engines, the Ford 120E was ground off and overstamped with 3020 leaving it as 3020 6015
2 Later Mk2 blocks (probably our TC ?) left the ford identification casting marks, he shows an example as 681F6015-A (which means nothing to me !)
3. The last blocks, presumably the 73 cars, also had Ford markings. He shows an example as 701M6015 EA (the E looks like a damaged B though ?)
Brian
