Ford RV Engine Issues

[CaneyCreek]

Ok so I just bought a 1994 Rockwood Class C RV with 17k miles on it for what I am hoping was a steal. It's been sitting in storage for the past 10 or so years and I got it towed back to my house a few weeks ago and have been going through everything. It has the 460 V8. Here's what's been done so far:
Oil change
air filter
fuel filter
Fuel pump
Fuel pressure regulator
battery
spark plugs (that was freaking hard)
Spark plug wires
Throttle position sensor
fuel injectors (bought some remanufactured ones because there were some mismatched 20lb and 24lb ones on there)
drained the old gas out (only about 5 gallons was in the tank)

So after doing all this I've been trying to get it running and am having some trouble. It will start and fire, but will not idle unless you give it a very slight touch on the gas pedal. Once you let off the gas it sputters and dies pretty quickly. I've checked pressure at the fuel rail and have a 37-40 psi when I turn the key to ON position. I have hooked up the OBD1 computer and got the 87 code back. The 87 code indicates Primary fuel pump circuit failure. I'm a little confused at where to go from here since the new fuel pump seems to be working hence the pressure at the fuel rail?? I've checked the inertia sensor and it does not appear to have been tripped, but for some reason the red and green wire going to it have been stripped (maybe the previous owner was having fuel pump issues before parking it??). Any ideas are greatly appreciated! Or if anyone knows any good mechanics that can come to me in Cypress that would be great.

Thanks

[bwguardian]

Is the 37-40 psi at the fuel rail with the engine on or off? The spec for it is 30-40 psi running, and 40-45 psi with the key on and engine off. It should have close to 30 psi at idle. To check the fuel pressure regulator, snap the throttle and the fuel pressure should jump to near 40 psi. You can also unplug the vacuum line from the regulator and then the pressure should be close to 40 psi. Does the RV have 1 or 2 tanks for fuel?

[CaneyCreek]

With key on and engine off it will be right at 40-42 psi. While it's running (with throttle) it will be around 37 psi. If I hit the throttle quickly the engine hesitates then revs up and holds around 37-40 psi.
It has a single tank behind the rear axle.
Also, after running it for a while and warming the engine up it doesn't want to start back up at all with or without throttle.