Need info on small briggs engine, flywheel swap.

I have a Briggs 3.5 Vertical shaft engine on 70's model Hahn tiller. Motor gave out, trying to find build kit, no luck. Question, Can I take the Heavy flywheel off this old Briggs (1983?) and put it on a newer Briggs mower engine? I am aware of the balance issue that mower engines use the blade as a counter balance for the lighter flywheel. But hoping I can find out if a flywheel swap is possible..thanks for any info