Bad idea heating up coils to lower it, this hardens the spring and makes it ride rough.
You also can't control the amount you lower a coilspring as well as if you measure,mark and cut it with a grinder or diamond blade on a recip saw.
As for the rear,if you don't plan on toting the full payload, just take out 1 leaf on each side.
Provided you only cut 1 full coil and remove 1 heavy leaf on each side,you should get a 2" drop that won't affect your chassis geometry or handling much, though you will lose some payload capacity.
-Heating up springs?-C'mon really?!!

 

I have a 98 silverado 4x4 if i did shackles in the back what could i do to the front ? just lower torsion bars? i heard that was bad though cause too low and itll ride the rubber stoppers on the a arms ??? help please

 

if i do shackles in the back what could i do to the front on a 4x4 just lower torsion bars ? also i heard lowering torsion bars too low itll rub on the rubber ***** of the a arms?

 

You have to get lowerin keys to lower a 4x4. Only way. And when you lower a truck they all ride on the stops unless it's with drop spindles on a 2wd.

 

2" drop shackles will level it out, initially. But if you remove the back bumper to install a roll pan, when that weight is removed, it will raise back up slightly. Which, is what happened to me. Now it has a rake again. Lowering blocks? Dont even go there....The best idea I seen on here so far is to have some 4" shackles made. The front? Spindles.