well if he wants boost then he has 2 options. I would still go aluminum as you wont be pumping enough boost to jeopardize either block. plus with more blower weight the iron block weight becomes even less desirable to me. to get the tq he wants he needs a PD blower not a procharger

A zl1 blower isnt a bad option but it needs recatnagle heads which need a 4" bore. So that means the op would have to source a more expensive ls3, l92 or ls2 shortblock and add heads. But a zl1 blower is a little cheaper than others.

If the op gets an ls1 or ls2 they can most likely use a gto or c5 maggie and the appropriate accessories. a used maggie kit wont be that much more than a zl1 kit. In the end i believe this will be the cheaper way to go. neither route is cheap however. In the end it will make very similar numbers in tq to the 455 but more hp with better streetability and mpg's.

Overall for the most "budget" friendly build I would get a used ls1/6 shortblock or even ls2 if he wants. Then get a set of low compression 317 heads and a ls9 gasket. Put it all together with arp bolts/studs and then run 10-12 lbs on it. Prediction for that would be 500+tq at 2500 rpm and then 500hp. 10-12 psi should live just fine with a good tune and 317 heads