Canadian C5-RA heads 39-41?

[Newc]

Hi all; I wonder about putting a pair of C5 iron heads on my Canadian C7 engine [59AB type]. First the C5 heads have been cut so as to have a 2 3/4" diameter dome [Small], then will the valve pockets clear the later eng's valve angle? All this dancing is for a '42 CMP Canadian truck. Thanks Newc