Gear Vendors in but big engine problems

If you're willing to farm work out which it sounds like you are, then you'd be hard pressed to find a better deal than an MP crate motor. Especially since you said were able to pull the engine out yourself. You coulda bought the motor and a case of beer for you and your buddies to help get the thing in.

These are on Mancini Racing's webstore as I write:

402 Magnum Crate Engine - 435 Horsepower
$6,099.00
MOPP5153527

406 Magnum Crate Engine - 435 Horsepower Magnum Block
Regular price: $7,119.00
Sale price: $6,495.00
MOPP5153474

IN STOCK READY TO SHIP TODAY!

And if you really need that magic 450, I'd bet there's prolly another 15 ponies in each of these things. Just a thought.