Let's hold on a cotton picker here......
The OP is getting a 318 and it needs rebuilt?
That's a LOT of money.
Might be cheaper to get a running driving (but may have trans issues) 5.2 and spend the money on the conversion accessories.
Sure will have an HP advantage right from the start.
In fact, a 5.9 will already be at that magical 300 HP number with ZERO mods.
...and should be good for about 200,000 total miles or more.