First question is what is your desired horsepower?
First bit of advice is to not bore/drill the cylinders any larger than absolutely necessary. The maximum should be 30,000s of an inch, but do not let your engine builder just do that as a standard approach. Keeping the cylinder walls as thick as possible is important for engine durability. You might need custom sized pistons but it doesn’t sound like you are on a restrictive budget
With your research you likely have some basic guidelines established. What are they?
Carburetor or EFI ?
Flat tappet hydraulic cam shaft or hydraulic roller or solid lifter ?
stroker engine?
Iron heads or aluminum ?
Intake manifold short enough to allow use of engine screen or are you willing to discard/modify the engine screen?
If you are seeking specific recommendations we need to better understand what you anticipate building
Larry