Easiest way is to sleeve your block and you know everything fits---when you start switching things something won't be right configuration---

And yep---I had 68 also --mine was one of the very first 428 CJ's----had about 100 miles on it when the smog stuff came off, cam change, etc---had a Holmon Moody Nascar 427 that I was gonna put in my 66 comet 390gt, Ford contacted me aout the 427 hydraulic moter early(late 67) and I was going to get one of them but they canceled and did the Cobra Jet thing--I was going to put the nascar 427 in the 68 but the CJ ran so good that I didn't--used it later in a pick up

Oh and not to hi jack----but putting a couple sleeves in a decent engine is no big thing--issue is what caused the crack--if it froze up in the winter-----I'd be real careful looking it over--