There will definitely be clearance issues.
The only thing to do here is to strip it down, clean out all the gunk from the block, crank, cams, check and if possible hone the cylinders, (if not, re-bore), polish or regrind the crank, and fit new bearings, pistons, rings, and a new timing kit and oil pump.
Then, pressure test the cylinder head, check, and re-seat all valves, and replace valve stem seals. Oh, and don't forget the tell the idiot not to do this again just after he pays you for all of the above.