Recording 4x12 peavey cab with jsx head

You don´t have many options so... just place the 57 in front of the cab, dial the best tone you can and record it. Compare to tones you like and chase it. The JSX is amazing, the stock speakers on the 5150 are very dificult to track IMO. All I ever got was fizzy, phasey and total lack of meat. Behringer is not API but again you have no options, you should get a decent sounding gtr with that rig.
 
do what andy suggested to me.......buy a couple V30 speakers and install it into your 5150 cab in an X-pattern. Like a ghetto Bogner! haha

but seriously.....

It will be a night and day difference!
 
Basically start by taking the SM57, and set it up in front of the cab, start like an inch away from the grill and point the mic like an inch off the centre of the speaker (the stock 5150 speakers have a really small centre, so you'll probably need a flashlight to make sure you have it in the right place). Set the amp up how you normally would EQ wise, then just track a few riffs, and see how it sounds, most good guitar tones only need a high/low pass eq on them, so don't try and make the sound good with a lot of post recording eq. Then just slowly tweak the settings on the amp till you get nearer the kind of tone you want. If you still can't get near the tone you want, then you have to take another direction and begin moving the mic. If you aren't able to have the amp up loud then you might need to move the mic up against the grill. Also experiment with having the mic pointed directly at the centre of the speaker this will give you more presence, but sometimes also more fizz in the high end. Also remember to try all the speakers in the cab, as some will sound better than others. Overall, just keep tweaking and trying, many of the guys on here have spent years just tweaking till they found a recorded tone they like, so don't worry if it seems to take you forever to find your perfect recorded tone.