Nothing. Alot more cylinder head/intake choices with the LA too.
If I had no engine at all I would go Magnum because they are easy to find. However in this case the OP has stumbled on to a hard to find LA roller which is the best of both worlds. Plus the 89 engine should have 308 casting heads which are supposed to be the best factory iron head. Just to clarify I would choose a magnum over a flat tapper LA block.
