The Sunbeam brakes are fine for general highway work. That includes the rear drums. It is very easy to overdo rear brakes when "upgrading". My brakes are real old time hot rod. Rotors from Pontiac Grand Prix, calipers S10, rears are second gen Miata calipers with Nissan Maxima rotors, with a 13/16th master cylinder and a modified 6:1 brake pedal. Would I do it all again? Probably not. It was a product of the products available, my mindset and input from Barry. Not really necessary. And although I shudder at the thought of all that cast iron flying around, I do got brakes!
Door latches on the Alpine are good, somewhat difficult (impossible?) to operate the same each and every time the door is opened or closed. But when latched, stay closed.
Don't worry about caster. It is easily and cheaply changed and does not change other settings. After you build the car the way you want it and don't like the way it goes down the road, start messing with caster. That's how I got to where I am. Cost was virtually nothing. I will tell anyone that cares to listen, my car was terrible when caster just south of 3 degrees. If your car is terrible and has to be herded down the road, change the caster.
Bill