I'm thinking of getting a 4x8 sheet of carbon fiber to do my door panels and rear bulkhead. Any suggestions on where to get it and what thickness to use? I want to get it with one side glossy.

Check with your local fiberglass shop... on the back
wall.. NHRA wants .032 alum.. so I would think the
same will work... its plenty strong enough at that
thickness but I dont know about fire

What do you plan on cutting it with?

I did my door panels etc from sheet I got at Tim McAmis. IF you watch they will do $50 off the full sheet price occasionally. It is not on sale now though

https://timmcamis.com/shop/4-x8-carbon-fiber-sheet.html

Not sure about the rear bulkhead thickness.

I used tungston carbide jigsaw blade, works great. Also some dremel cutting wheels, but they tend to break often. Clean up the edges with sanding block etc and you can run a sharpie along the cut edge to recolor it black. Make sure to wear full protection on skin and use a respirator.

I cut my carbon wing with a regular ole jig saw

I did all my trim work on my CF hood with a jig saw
and a .040X4" cut off wheel on my air grinder

You can buy door panel size pieces onot ebay

Buying a full sheet is cheaper.

Carbon fiber is a general term. Just like there are many weaves and grades of fiberglass so too for CF. Many pitfalls when buying the product. Go to a fiberglass supplier. They have lists of the products available. You are better off buying CF that has epoxy in it. In order for the CF to be strong, it must be thoroughly wetted with epoxy. This is where most people screw up. You also need a vacuum press for complete saturation, air bubble removal ans moldability. Be wary of sheets that come from over seas, their quality is always suspect. Use a cut off wheel. It does not leave loose strands.

Is the objective here cosmetics, insulation, strength/stiffness and/or spending money?

I got a blem a few years ago from Unlimited Products and it came shiney on one side but I hid mine behind speaker material............I cut it w/upholstery scissors..........

Ultracarbon sells it buy the sheet. Its far from cheap but you wont find a better quality..

http://www.ultra-carbon.com/products/4x8-carbon-fiber-flat-sheets/

Well its a race car so the main objective is to spend $ I guess ;-), lol. No mainly its for cosmetics. I'm redoing my car this winter and would like to do it the way I want it at this time. I'm tired of doing it to just get by and redoing stuff a year or two later. It'd be an added bonus if it reduces weight also. Looking for opinions and advice.

At least you aren't in denial.

It is a pretty cool material to work with if its affordable, for its physical properties.

A straight 8 harness, 14 mil cloth wetted out with EA956, 2 plies, cured under vacuum will make a nice flat sheet to do door panels and trim parts with. The 14 mil twill weave is what you see a lot of as it looks fancier, but isn't any stronger than a straight weave. You would need a flat table, release film, Tedlar, A 4000, then a bleeder separator, perforated A 4000 or CHR III then bleeder cloth, then another layer of A4000 or Tedlar, breather material, either Felters N10 or #1000 glass, Tacky Tape and bagging film, and a vacuum pump.

Buy it from McAmis, Haas, Jones etc and it will be the nice lite weight race carbon

Not sure where you are located but I have two buddies that make carbon out here in the west. Can get you info if you like.

I think I'd be better off to buy it done, lol. I've got no experience with carbon fiber or fiberglass.

I live in northern Minnesota. I'll have to pay shipping no matter where I get it