Regarding the firewall, the left cylinder bank will not clear the firewall and it will have to be dimpled to provide clearance. It isn't that big a problem, but it has to be done.
I don't think the HEI distributer will clear the firewall, but the older distributers, such as mine from a 67 engine, clear with no problem. It isn't the easiest to work on, but it would be no different than the location of the distributer of the small block V8. ( I had previously swapped 2 small blocks into these truck chassis )
Bob
