3869942 was the good 427 block but it came with 2 and 4 bolt mains. Weiand used to make a fair intake for these with oval as well as rectangle port
Either crank 454 or 427 will fit but you must use the flex plate or flywheel and harmonic balancer for that crank. 427 is internal balance and 454 is external. Here is the rub,you have a half inch of cylinder bore length to make up one way or another if you use 454 crank. On mine, I chose to get 1/4 inch from stroke and 1/4 inch from rods because I had big buck pistons and needed the up grade in the rods. you have several options. more stroke to 1/2 inch, lower pin position on pistons or longer rods. The combinations are abundant. For my purposes I found I had head gasket problems with the 1/2 inch stroke and rod breakage with stock rods. It was the logical choice. I don't think they made rods long enough at that time. You will have to get your calculator out to find a happy place for you.