Bled the lines and still no brake pressure

No I haven't. My brakes used to be fine till I noticed a leak in the lines connecting to the lspv so I replaced the lspv and lines connecting to it (it was too rusted to save) then bled the system and I can't get the pedal firm. If I pump it I can but like I said it sinks to the floor slowly

 

Right, so that will help you localize which circuit, and which component(s) are at fault.

 

Go around the truck and line-lock each corner. See if the pedal gets firm

 

If it pumps up then sinks, this sometimes is a sign of drums being out of adjustment… I’m sure you’ve checked it. But just something to consider

 

Viagra?

..sorry.

 

long post so bear with me...

first thing is to check that the brake master cylinder push rod has some free play. If the spool valve on the master does not return fully the lip seal on the spool valve will not open up past the charge port, this is where the fluid from the reservoir will fill the master cylinder, there are 2 of these. check you rear shoe adjustment, it should just barley / hear a drag from the shoes. If that is not the problem, with the vacuum bleed off the booster, push on the brake pedal a few times to expand the rear shoes until they touch the drum then quickly push the brake pedal down and hold the pressure, do not let up on the pedal, if the pedal slowly starts to drop the master cylinder is defective or there is an external leak. Just because it is new doesn't mean that it is good.
if it passes these tests I would buy a 1 foot length of the correct thread and flared metal brake for the outlet of the master cylinder. Cut a 4 inch piece of brake line, slide the flare nut to the flared end of the brake line and bend the open end over on itself once or twice and smash that end closed with a hammer, do this for 2 separate lines. Install these on the output of the master cylinder and have someone slowly push the pedal and loosen the flare and bleed the air out. Now step on the pedal it should be rock hard. start the truck and see what the pedal feels like. If it passes this test take one of your test lines off and hook up the factory line and as suggested above see if you can isolate it to a particular hydraulic circuit. The flex lines could be so pliable that they are just ballooning under the pressure.