It will sure help the rest of us if we knew what engine you are talking about here - and why you want to do this the hard way.
If it is an old school American V8 then intake manifolds and carburetors are readily available.
If it is an in-line 4-cylinder then some enterprising people have adapted motorcycle carburetors to them.
If you want fuel injection then question 1: what's wrong with the vehicle's stock ECU? question 2: MoTeC, Magnetti-Marelli, Megasquirt/Microsquirt, etc.
Yes, this stuff costs money.
Re-inventing a wheel that has already been invented long ago, costs more.
Half-arse-ing it because you don't/can't/refuse to do it the right way, is a sunk cost when it doesn't work right and you end up having to do it again, the right way.