360 heads on a LA 318 vs Magnum heads on a LA 318

Slantsix64 said
360 heads on a stock 318 equals really low compression probably in the 7:2:1 range, pretty much loss of low end but you gain high end.

but keep in mind the roller La 318 had taller pistons and actually were 0.040 in the hole. In the ones i took a part, those 360 heads are like 72CC mill them down .040 probably get you in the 68cc area Advance that camshaft 4 degrees or more to build up some pressure run a thin *** head gasket you might be alright, then again depends on your camshaft and rear gears also.

I don't have any knowledge of the magnum heads, but I've heard that they are prone to cracking next to the valve seats, my question is if they crack next to the valve seats won't this only get worse? Will the cracking cause the valve seats to come out? Also I just looked up what edelbrock performer rpm heads for a sbm would cost and was surprised to see that they are around $200 a pair cheaper than promaxx heads.