360 Roller Build - Advice, etc. (Lengthy)

Well. Every car is a death trap with idiot driving.

Double pumpers are made by Holley only.
Eagle stuff is dirt cheap for a reason.
Well ported Edelbrock heads will flow 300 or danm close with the stock valves.
If you really NEED to say I actually have a head that flows 300 cfm, check out Hughesengines.com.
The carb size is determined by the over all package and goal. 750 is fine. 830 more top end HP, but not really a lot more. Some fellas here run carb cfm's into the 900 area.
Stock oil pump and water pump will do.
Serpentine set ups on the engines do not use a 4th belt tightening device. Tighten it up with the Alternator like normal.

Transmission; dead stock with a twin pressure plate set up for dropping clutches at high rpm. Use a Lakewood scatter shield & driveshaft loop.
Bogging off the line is one of two things. Poor tune/set up or idiot behind the wheel.
Stick with the iron case.

Nothing about your (long winded) post suggests anything about weight reduction. Nothing.
All the "Hot Rod" parts that are lighter via the material there made with is a common thing to find on street cruisers.

You want weight reduction?!?!?!
Hot Rod magazine did a Duster with just that single goal in mind. The link I do not have handy but it has been posted here several times. Besides the basic fiberglass everything, they also did Lexan windows, aluminum center section on the rear, tube K frame and attaching parts. Do a search here or at Hot Rod for it and see what weight reduction is really about.

I think it was Hot Rod that also had a write up with Herb McCandles who did a 372 to 500HP. This is when the Edelbrock heads were new, so yea! It's been awhile, but it's been done a long time ago.

Generally speaking, I like your combo but do not know for sure if you will reach the 500 hp goal. A lot of it is also in the actual machining, part prep and assembling of the engine.
Lastly, in trying to address everything you wrote (Whew! LOL!)

Zero deck the pistons. I had run my 360 this way with a smaller cam and pump gas was OK with it. Also a 4spd car. E body though.

Enjoy!