We have 17 rides in the shop right now, three restorations and 14 resto/street rods. There is a common theme among the non original ones that I think offers a lesson that should be followed for a successful and safe build. No sophisticated math for various components but just stuff a home builder can do to make a difference in a driving/riding pleasure and an unfinished project on Craigslist.
# 1 BRAKES:
You can have very good drum brakes but if the ride is going to be an all weather one then front discs are time well spent. I ran drums with power assist on my 37 Buick for 25 trouble free years UNTIL I was in Kansas City during a monsoon and rush hour. With the right side drums being under water I had full pedal and no brakes. Discs are unaffected by water, dirt, mud, heat.
#2 Tires:
Radials stay flat to road surface for max traction and best of all don't get "squirrely" on grooved pavement. Many areas have the grooves to drain water and cut chances of hydroplaning.
#3 12v negative ground:
Without special order this is what all after market "toys" are set up for. I'm cheap so being able to buy an alternator with a life time guarantee for less than single generator component is appealing.
#4 High pressure cooling system:
Everyone wants to add creature comforts to their Dream so a system that boils at 212* is best suited for the trash bin. A 15# cap boosts the bp to almost 260* which if that doesn't work you have troubles.
With these basics you can then play with height, stance, suspension (from couch soft to chip tooth enamel harsh), wiper choice, sound system, power everything, engines from lap Poodle domicile to belch fire V's with 1500hp.
With the four basics for at least a safe ride there is a good chance you will get enjoyment from your Baby while all the rest can be chalked up as lessons learned for both you and your billfold.
Finally:
Feel free to ad any other gems of success YOU have learned.