I'm trying to get the stock crankshaft pully off but it spins when I try to loosen it, any tips/tricks? thanks

 

An impact would work but I assume you dont have one. Put your socket and ratchet on and use a hammer to "shock" the bolt loose. Tap the ratchet with the hammer and it should work out for you. Not the number one choice but when you don't have the proper tools you gotta improvise.

 

Tried, but the impact I have isn't budging it, it's rated at 90psi max, do you think PB blaster (penetrating agent like WD-40) would help out?

 

Just get a second set of hands(not your wife or G/F)to hold onto that pulley and hit the ratchet with a hammer, she'll turn loose.

 

Put the car in gear