Making power out of the 318
It would be wise to build the 318, if it was a complete running motor but it's a basket case that is missing parts and will likely need some machine work. Since it's likely to be cheaper for him to buy a known OK motor than even assemble what he's got, it just makes sense.
The kid is still going to need a bunch more stuff to complete a V8 swap into a slant car, so keeping it thrifty has to be the main goal. Getting 400+ out of a 318 isn't hard, but getting there from where he is will be a steeper hill than grabbing a $500 Magnum and a busted $500 LA with an airgap or street dominator and headers or something on it already..
I mean, the right pistons to support his end goal will cost as much anyway.