single cam boost or ls swap ?

[Formally...]

and slinging rods

Ls boosted would make more power then a sohc boosted anyday!

But to the OP I would do a LS swap and turbo later

Slinging rods

Okay the LS TURBO (not NA LS like OP said) could make about 30-50whp more stock then a dseries but you have to factor in the price of a tranny, axles, shift linkage. etc

The dseries is plenty strong. Scotty (scttydb411) has tried many times to blow his BONE STOCK 140k mile Y7 up on the dyno and it is still going strong (255whp). I have turned up the boost on my daily to 15psi when it was only tuned for 9psi (motor was already making funny noise and i didn't care). Still made 220whp the day I pulled it out.