cracked 273 heads

what caused the problem in the first place? other heads will work, one of the best heads is the 1988-91 318 swirl casting #302 head with around a 60 cc chamber. most other 318 heads are around 64 cc - compression lowering chamber, except the 1967 318 casting #2658920 with a 57 cc chamber. the 1965 intake can be ground or machined around the bolt holes to bolt onto later heads