Nice square dude!!! It's not spray (but I think it can be sprayed with the right nozzle) but I undercoated mine ('77 C-10) with POR 15 and it's great stuff! Goes on really smooth and dries really hard.
The good thing with POR is that it's easy to use. However, when you use it you may want to wear long sleeves, gloves and long pants. Whatever you get it on will not come off and that includes clothes and skin (until it wears off). It's kind of pricey but it spreads really well so a little bit goes a LONG ways. Also, it's made to go over rust so no need to blast the frame or under part of the body completely clean. When doing mine I just knocked off the loose rust and first layer of rust off with a wheel and applied the POR 15. It went on smooth and has held up very well.