Is 16 ga. thick enough?

It seems like once everything was boxed in it would be plenty strong but I have no experience in this area......

 

 

You'd be much better off using tubing, for many reasons. If a square or rectangular cross section, I think you'd need to be at least 12 or even 10 ga. to prevent flexing under vacuum.

 

Aluminum or steel?

I'm going to be building my own 3-2V intake and long tube headers for my 300. I'm going with a common/single mounting flange. So I'm going with 14 ga. c.r. steel with 1/2" mounting flange and carb bases. But everyone I talk to about my intake says it's big time overkill.

If you are going steel I think 16 ga. should be fine. If you are worried go 14 gauge.

If it's aluminum you might want to go 14 ga. or maybe even thicker. If I remember right you plan to mount a blower to your intake right? If you are I'd consider all that weight sitting on it. Even with thicker material I'd still add some support brackets along the intake and on the snout of the blower.

 

A friend of mine built his intake from thin wall square tubing....seems to work pretty good. 261 Chevy 6/with 3-53 blower.

 

I have built a few from round and square tubing, but round flows better as the flow rotates around the perimiter of the tube. Sheet metal would be harder to get equal flow with, but if you install multi-port fuel injectors that won't matter much.
here's a funny one i built to put a 2 Bbl Weber on an old goldwing motorcycle with a flat 4 engine. I lined the inside with fuel-proof Red-Kote tank liner to make sure it was sealed completely

 

Check with offenhauser... they have some pretty sweet intakes for the 300. you may find what you are looking for or even a better starting point than scratch.