mustang help.

[8bangin302]

ive got a 94 mustang,it will crank but has a hard time doing it,and if i run or drive it a while it wont crank up,it will turnover but wont crank,i just replaced the battery,fixed the bad cable that it had and terminal,cleaned both terminals also..what could it be the alternator,maybe i didnt fix the cables right, what?
much help will be appreciated..
thanks

also i just bought an aftermarket seat from the summit,i need to install it but dont know how,i know how to take the stock seat out and put another one back in,but the guy said it might need some fabrication and i need to know what i need to do..
thanks