150 HP LA 318 - vs - 230 HP Magnum 318
Your welcome, although the 5.9 isn't something that's to be skeptical about, it's sure fire. :D
I'd keep you 318 till it blows up, then replace it with a bigger motor if your satisfied. When your ready, check a truck junkyard in PDX or something when you get ready to rock. This way, you can take your time and collect your parts.
http://www.forabodiesonly.com/mopar/showthread.php?t=201632
Inspration!