Early A10 engine with later aluminium head either 276 or 376 will not fit into

[Tom]

I have a 1952 A10 basket case which I am restoring.  I fitted a later aluminium head/rockers/covers etc instead of the iron head thinking it would be better!   Engine fits into the plunger frame but neither a 276 Amal or a 376 will fit.  Is there any solution apart from reverting back to the original iron head?
I live on the Prairies of Canada and spring has just sprung after a long, brutal winter and I would love to ride the old Golden Flash this summer!

[AWJDThumper]

In what way don't the carbs fit?

[STAR TWIN]

It's back to the iron head. The only alloy head which will fit your bike is a twin carb one - rare as hens teeth.