Trying to decide on the whole gas tank thing.
My truck is going to be a lowered darksider, I am okay with the fill in the truck bed prefer to mount it behind the axle. I would like to run a stockish bumper with the brackets trimmed to bring it higher and closer to the bed. I would like the exhaust tips to come out under the rear bumper.
Does the exhaust (dual) typically run under the tank? or between the tank and rear leafs.

How low is it okay for the tank to be under the bottom of the rear frame rails?

 

I used a small 65 Mustang tank on mine and mounted it in betweem the frame rails and inside the frame channel. I made a 1" square tube frame to mount it on so that raised it 1". It only hangs down 3 or 4 inches under the frame. I don't know how low you are wanting to go.
I run my exhaust out the side but there is room between the tank and Springs.

 

The "hugger bumper brackets" are available from a few vendors. Mid Fifty wants $100 a set for them. John' F-Fun Hundreds was less (I forget how much). Or, you can make your own. I have pics and drawings (last 4 frames) in this gallery: https://www.ford-trucks.com/user_gal...&albumid=12266

Fuul- length exhaust systems with rear tank usually run over the rear axle, under the shock crossmember, and out the back under the frame rails. If you don't run the pipes that far outboard, you'll have to drop the exhaust system to drop the tank. Hanging the pipes is really easy under the frame rail, too.

Clearance between pipes and tank can be a small as 1-2", as the pipes are pretty cool by the time they get that far back.

 

I ended up with the 20 gal Mustang tank under my 56 before I sold it. Used a 1" tube frame to mount it. Not much room for exhaust when the tank is mounted in the rear. You can see some photos of the tank frame in my gallery.

 

I also mounted 74 Mustang tank in my 50 F1; was more comfortable running dual exhaust out side behind running boards.

Tom

 

I used a Summit Racing Fuel cell. Fit good between the frame and only had to move the rear support about a inch. Made my own hangers out of flat stock and rubber coated them.

 

What I like about the Mustang gas tank is that the fuel line does not come directly out of the bottom of the tank. The previous owner of my 54 installed an aluminum deisel tank of unknown origin in the rear of my truck. The truck was also bagged all the way around. The tank sat very low and the fuel line exited at the lowest point of the tank. Well of course MURPHYS LAW took effect and the rear air bags failed one day while I was driving. It tore off the fuel line and the truck sat stuck in the leaking fuel. I'm installing a mustang tank right now.

 

rustfarmer, you really oughta get a gallery so we could help by means of moral support...
that truck looks killer btw. I, for one, would like to see more of it.
back on topic - I've planned on the stang tank too, but have yet to get there.