Will the later model efi windsor motors go into the XM/P without any bonnet mods or will there be clearance issues with the upper manifold thing plenum(?) and the bonnet underside?
Thanks

You'll possibly need to change braces alittle ??

302w...no problems
351w...problems.
As EBXR says tower braces can get in the way a bit.
Front serpentine drive on EB-up 5.0's will have clearance problems between some accessories and the front of your left shock tower(see my 351w into XE article). '86-'93 5.0 mustang or 5.0 F-series serpentine drives fit better although they also stick out further.

Pete.