Smallblock V8's are very versatile, with a lot of options available to someone who is willing to mix and match parts and/or do some custom machining. I was fitting aftermarket 4-bolt main bearing caps to 305 blocks back when I was dealing with cubic inch and/or carburetor restrictions, changing connecting rod lengths, angle-milling cylinder heads for higher compression with heads with "legal" casting numbers, and doing a bunch of other quasi-legal stuff to get a hot-rodded engine through the tech line. It was a constant battle of wits with the tech inspectors, but a lot of them came to the game poorly-armed! LOL!
Jerry
