Re: edelbrock and lpg
Going from the title of your thread you were thinking about Edelbrock heads. Problem is Edelbrock don't make Cleveland heads. Look for CHI or AFD for alloy Cleveland heads.
The Impco 425 bolts onto a holley throttle/base plate.
It sounds like a bit of a waste to put decent alloy heads on a motor that can be fed by a single Impco 425(ie sub 350hp). Your iron heads can easily achieve that kind of power without much work.
1980 Falcon ESP - 351
1973 Plymouth 'Cuda - 340