Basically, 2 limitations, both serious.
1. without a 12 port head ($$$), big peak power is difficult (compared to a modern V8 head). Lumps + valves + extensive porting.
2. make sure nothing breaks, 1st parts are rods and pistons.
Santucci is surprisingly brief in his discussion of the oil system, especially oil and pressure control in the pan. Look at other L6 engines for ideas.
