hope this info helps
http://www.moddedmustangs.com/forums/99-04/198431-return-vs-returnless-fuel-system.html
post#2 of a similar discussion

If you are keeping within a reasonable hp level a returnless setup will work, but a return style is better because it can cope better with a sudden demand for lots of fuel without losing as much fuel pressure.

 

Foush, the pumps themselves are not interchangeable. You should not use a return style pump in a returnless system. A returnless system uses pulse width modulation to vary pump speed and pressure. Walbro and other return pumps will fail prematurely in a returnless because of this. Swapping to a return style isn't really difficult, it's pretty straight forward, except your tuner has to take it into account so the tune isn't expecting to change pressure, and instead only reads it. Like Vince said, once you get into higher horsepower it would probably be easy to convert. You can get a returnless to work with high horsepower but it starts getting very expensive compared to returnless - basically you end up having to buy a lot of excess capacity to minimize pressure loss... easier to swap to a return system.

 

First thing is upgrade the wiring to the fuel pump with a thicker gauge. That will help lower duty cycle. As far as cheapest, if it weren't an F150 I'd say get a dual pump fuel hat, but for the F150 they are darned expensive and you might want to consider a Kenne Bell Boost A Pump.