I just brought an XD falky panel van and it rocks!!
It started life as a 6 but the previous owner dropped a 302C with a holley 600 vac sec, pacemaker headers and a cam. Pics here http://www.fordforums.com/showthread.php?t=61936
except it now has chrome rocker covers and an MSD blaster 2 coil. I got a 3 inch 2 - 1 exhaust an put it on the dyno (180hp 220 ft-lbs). In the not to distant futre it's getting new shocks, bushes, dropped a coupla inches and a paint job...red I think.
It would be an easy swap to do (not that I've done it) as you can get all the parts you need from a doner V8 car, it should be as bolt in as you can get!
I'm also in the middle of putting a nissan 3L quad cam twin turbo in to my Mk1 capri, it should be an honest 300 rwhp. This is about as far away from a bolt in as you can get, unless you or a good friend are good at fabricating parts think carefully before you do it as grafting an engine in is a big job but that also means the end result is a bigger buzz!
If you are going for a van that's going to be mainly road use I'd super charge it. I have turbo'ed and supercharged capri 2L engines and my favorite for the road is the blower.
Good luck on what ever you go for!