4.6 P38's can be purchased for ~£720 (that's what I paid and I wasn't trying hard to find the cheapest), scrap the rest you can get plenty back (possibly even turn a profit) if you can be bothered to sell parts. 4.0's are as plentiful as they're in D2's as well.
LSx's can be had used for $2000 plus shipping, and it's hard to find anything LS that makes less than 300hp and a million torques. $5k+ puts you into new crate motor territory and $10k puts you into big numbers everywhere. Plus they are ubiquitous stateside so gearboxes, ECU's, upgrades, etc. are very available, they're the modern small-block-chevy and made in their millions.