I would go with a rebuilt engine. You can find a core from you local junk yard and rebuilt that or buy one already built.
If you will be adding a power adder later(nitrous, blower, turbo) go with forged pisons. If you won't be adding one hyperutetic will be fine.
Can you do some of the work yourself (ie. install heads, intake, exc.)? If so you can probabley build a strong engine for around $2,000.
www.rangerstation.com has some good information about V-8 swaps.