Agree with Duntov 100%. Bolt the headers on the motor and drop it in the hole. Cut out anything that's in the way. Weld pieces back in to cover up the holes after you have placed the motor. If you have to cut out a crossmember, then cut it out and re-build another crossmember farther forward or rearward. You're the boss. Do whatever you want to or have to in order to get the motor in the truck.
As far as the electric fuel pump, mount it as close to the tank as possible and as low as possible without getting it in harm's way from junk on the freeway. Mount the pump to rubber, then mount the rubber to the truck frame or crossmember. I use the black rubber that comes as a muffler mount. It is about 1" by 3/4" and has holes in it. Cut the rubber from the steel part of the muffler mount. Mount the rubber to the truck, then mount the pump to the rubber. I had trouble trying to find such an animal when I was googling for a photo of these hangers. Maybe they don't make them any more. At any rate, use some good sturdy rubber pieces to mount the pump.
Here's a good pump to use.
It's factory set for 4 psi.
This pump is set at 6 psi and may work. The pressure will drop a little through the run of fuel line from the pump to the carb, so this pump may work as well....
YOU NEED ONLY 5 PSI MAX AT THE CARB INLET. Higher pressure than that will overpower the needle and seat in the carb and blow raw fuel into the intake manifold. You will never get the motor tuned with this going on. This 4070LP is a low-pressure, high-volume pump, so run a 1/2 inch fuel line from the tank to the filter and from the filter to the pump and from the pump to the carburetor. The fittings on the pump and the filter will be 3/8 inch. Use adapters to 1/2 inch and run 1/2 inch line tank to the carb.
You want to mount a cartridge or spin-on fuel filter right at the tank first, then the pump immediately after the filter. Use a short connector piece of QUALITY fuel hose instead of solid connections at the pump, both on the inlet side and the outlet side of the pump. Solid connections will drone constantly and make you nuts from the sound. That's why you mount the pump in rubber. YOU NEED ONLY 5 PSI MAX AT THE CARB INLET. Higher pressure than that will overpower the needle and seat in the carb and blow raw fuel into the intake manifold. You will never get the motor tuned with this going on.
Do not use that fosdick black rubber hose for making your connections between parts. Use only quality hose specified for fuel use.
Here are some of the quality hoses I'm talking about....You'll find other makes and specs at....for instance....NAPA.... (Genuine Parts Co).
Aeroquip Star Lite 200
Fragola Performance Systems Series 8000 Push-Lite race hose
Gates LOL Plus
Russell Twist-Loc 836
Russell XRP HS-79
Dayco Imperial Nylo-seal tubing
Goodridge 536 & 710
Or any other kind of premium quality fuel line hose. I just don't want you to use the cheapo, fosdick black rubber hose that will deteriorate and rupture or leak. Sometimes, that stuff breaks down inside and will block fuel flow. You can't see it, so you can't find the problem. Or a piece of it will find its way between the needle and seat in the float bowl.
I might use a cartridge filter such as this one...
That uses these replacement filters...
There are hundreds of different pumps, filters, etc. that you could use. I'm simply showing some examples of parts that I know will work for you.
The whole idea here is to filter the fuel before it gets to the pump and use a pump that will produce sufficient pressure and volume through a 1/2 inch line so as to eliminate the need for an inline regulator to bring the fuel pressure down to a point that it will not overload the needle and seat in the float bowl.
Here's a roll of 1/2 inch aluminum line like used on drag race cars. I see this stuff on every other car that comes through tech inspection....
Secure the line to the frame every 12 inches with insulated Adel clamps such as these...
Ace Hardware has these in several sizes.