If you are looking to do it cheaply thango with the Herculiner. Since the inside of cabs get little if any abuse, the herculiner should last for nearly ever, except around the door sills where it will get the most wear. I used it on my sliders, it gets worn down where my shoes scuff the slider when getting in and out of the truck. To do the floor of a std cab, a half gallon should be enough for 2-3 coats, and shouldn't run more than about $60.

More than tread lightly. Leave it like you were never there, nor anyone else.
'90 X-cab 4.88's 33 BFG AT's, rr ARB, Headers, Ignition upgrade, cold air induction.
'91 X-cab 5.29's 315's BFG MT's, rr ARB, custom bumper and flatbed