will the stock water pump circulate enough water to put my radiator behind the cab or do I need a high flow one. never did it it before and I'm kind of a broke ass so don't want to buy parts I don't have to. thanks

Yes it will I have had mine mounted in the back for a couple years.  Tip the radiator top has to be mounted higher than you engine for p[roper circulation

Has anyone ever had trouble getting the air to bleed out after they put the radiator in the back like that? 

Not if you be sure to mount the top of the radiator higher than the thermostat.

thanks guys

you can also mount it low in the bed, out of the way of mud and run a degas bottle in the engine compartment or on a roll bar, that will keep the air out and allow it to circulate just fine, and theres plenty of aftermarket ones, most newer vehicles run them since the radiators sit so low on the front end. 

I have my radiator in the bed and I still have a stock water pump. I've never had a problem with it yet. I've never had a problem with bleeding the air out either. And the exhaust pipe for water lines is a good idea but eventually the pipe will crack horizontally. I used 1 1/2 black pipe it takes a lot of time if it is installed correctly but you should'nt have any problems with it. If you do run the 1 1/2 water line caterpillar sells some good clamps to mount it down good. Part numbers are 8T-2525-Grommet 5P-7468-Clamp 5P-7469-Clamp. Good Luck!

i used fence post