I don't think for 60k you could do merc unless its a 496ho. I think oem on the 525efi w/xr is like 32-33k. Now if you fid a set of low hour used ones maybe. Now custom I don't know most of the ones I have seen in the 550hp range want about 25k just for the motor. It look like 25-35k just for the drives,gauges,bolsters,k planes etc.