4 inch stroker cam size question

I originally built this motor with a 5.9 Magnum block(don't ask what I was even thinking) with the zero deck and the biggest magnum head style combustion chamber we were at about 12.5 to 13 to 1 on compression. Probably would have been a BMF in a drag car, but I wasn't building a drag car. My buddy runs a machine shop and he's in the process of machining a 1971 360 block for me right now so I can swap my rotating assembly into it. Maybe we can back off the zero deck enough to drop the compression to a usable level.