I'm not sure I have the patience / time to build 4 gearboxes.
My goals would be to have a first gear that is usable and the ability to cruise at 75mph on the highway. With my existing 4 speed, I have a 3.78 main shaft and a 3.88 R&P. I'm running the standard old stock 67 sedan gearing with 185/65's. I feel like I don't get but 25-30 feet before I'm shifting into second. I understand that aftermarket first, second, third and fourth gears get expensive, real quickly.
I also feel that it is impossible to try a lot of different ratios so best guess is what you usually decide on, depending on advice but in the end you might have to build 4 trannies before you get the one you liked if you have that privelege or opportunity. I guess for that your name has to be Stanislaw Ray
I'd feel I was being besmirched, if it wasn't all true. I keep telling everybody not to be like stupid-Stan, trying to make a silk purse from a sow's ear. Just get the 5-speed, get it built right from the start, and don't dork around trying to make something with less than 200 lb/ft of torque be perfectly geared for all terrain with only 4 gears.
V8s ran 2-speed powerglides in the '60s and got away with it-- but they had the world's slushiest torque-converters and engines that produced a few hundred lb/ft of torque at about 1500 RPM. Modern performance cars have about 8 gears. My wife's minivan has 7. I don't think 5 is asking too much.
Every time I hear a guy talking about how a 4-speed can be the poor-man's 5-speed, I wonder what planet he's from. Getting the "almost as good as a 5-speed" 4 -speed means trying a bunch of different gear-sets until you get a spread you like. Sort of. Usually. Until you are behind a log truck in the mountains and you're in that really bad spot where third is too short and fourth is too long.
I have a box I like, but it's my 3rd try. Not everybody is wired to beat their head against the wall until either the wall or their head breaks. Fortunately (or not, depending on how sensible one is), I've got a pretty thick head, so the wall eventually gave way.
Just get the 5-speed and be happy.