I believe the cloth is an option on the ST, AC is standard on all trucks now I believe. You can do aftermarket windows/locks/cruise, but most look like the afterthought they are. By the time you add the aftermarket windows, locks, cruise, etc. the "savings" of the SLT is gone, and you still take the depreciation hit for the ST vs SLT.
Go with the SLT, it's a much nicer package. Resale is also significantly better on the SLT than ST.