devin -
For that power level, make sure you get quality.
Are you looking for small block, big block, normally aspirated, forced induction, EFI, intercooled ?
I would contact Nelson Racing Engines,
www.nelsonracingengines.com, they build great stuff.
Other good recommendations I have seen on this board are:
Bill Mitchell -
www.theengineshop.com
American Speed -
www.amerspeed.com (small blocks only)
Scott Shafiroff -
www.shafiroff.com
Ones that people said to avoid:
Speed-O-Motive
Some factory GM crate engines.