any engineer will have a look/measure for you
if its just a basic standard build then by all means have a go
they are old engines and so very basic realy
just dont go trying to go for much more than standard power or this will get harder
bit more involved when you got porting, mod'd valve seats, cams to time/dial etc
but as i say take more time than realy needed and triple check everything
and lub everything up proberly, i.e pistons, cam journals, big and small ends, mains etc