If you want fuel injection and want to be above the norm, why not try the Vortec 4200/GM Atlas LL8. It's an inline 6 and the later models (up through 2009 according to Wikipedia) were knocking on the door of 300HP. I've seen posts on here in the Hi Po forum about the swap. Might be worth a look.
Of course, call me old fashioned, but these days the most above the norm thing to do with a classic truck is to keep a Stovebolt in it. :-) Nobody does that anymore....
