It's probably the easiest engine swap if you're trying to go to something larger but there are good points to adding a V-6 over a V-8. If that is the route he decides then yes the 4.3 V-6 is a good option. Just will take more work than a magnum.
When I still had my 2.5 I looked at the stroker kits and turbo kits. I almost bought an Avenger supercharger while I was deployed to Iraq. One popped up on Ebay but was missing some parts so I was trying to get a hold of Avenger first to make sure I could get the missing parts and it sold.
I was looking for a Dakota bellhousing to swap in a AX-15 which was how I'd ended up calling Backwoods Off-Road who did my V-8 swap. And after talking to him he convinced me to forget the turbo or supercharger idea and just go V-8. Can't say it was the best choice but I do enjoy the V-8.