I think this largely depends on you and your goals for the project. Example, if it’s a drive around town stoplight to stoplight cruiser that’s largely going to see 0-45 or whatever, that’s whole different setup than something that’s going to do longer cruises at highway speeds. The former you can run around with an older 3 speed trans no problem, the latter would really benefit from overdrive. Other people might be completely fine spinning 3k+ rpm going down the road. That’s kind of where you have to figure out what you want and what fits best. I’m not trying to assume you’ve got an old American vehicle, just wanted to use it as an easy example.

Here’s how I go about mine. I have both a broad idea of what I want in the end, and I have a minimum threshold of where I’d start driving it. There’s usually a pretty wide gap between these two points and my broad end goal tends to change somewhat as I get through some of the work. I get to that minimum threshold, which gets it on the road, and see how it is. After I drive it for a while and work out any issues I ask myself what things from my end goal would I like the most right now? I consider things budget constraints, time, difficulties involved in next steps, things like whether I have to solve other problems to tackle the problem I want to fix right now, basically any “known known” I can. That guides me in most of my decision making.

I’m a firm believer in just getting the damn thing on the road, then work on it as time/budget etc. allow you to. I’ve got friends and family that have been working on their projects for literally decades to get it “perfect” meanwhile I’m enjoying thrashing mine around corners or doing donuts in empty parking lots. Paints fucked? Still makes tire smoke. Wheels aren’t the ones I want? Can’t see them from the driver seat. IMO cars are meant to be enjoyed on the road, not sitting in a shop getting never ending work and upgrades.