I don't need more power in my '68 M-715.  I want it.

I've been enjoying my '68 M-715, aka The Evil Truck so far this summer. It's been too hot for a desert trip, but the family enjoys taking it on cruise nights, to ice cream runs, and even for kids' birthday parties. Just yesterday I was ferrying preschoolers around the neighborhood for my son's 4th birthday party. But even though the GM Performance Parts 290hp/350 crate enigine has no problem motivating my antique army truck, I've suddenly found myself whipping up parts combos that will get my an extra 100-120hp and a whole lot more torque across the board.

I don't really want to crack into the little engine. Hell, I've got enough non-running projects I need to mess with. I shouldn't be tearing a perfectly good, running vehicle apart in my driveway. But there's that little voice in the back of my head......

So how about it?  Would anybody want to see how to bump up GM's least expensive $1,700 long block crate engine to 400-420hp without sacrificing power or torque anywhere in the powerband?