A buddy of mine has a 90 suburban wont start now due to the fact he threw in a new battery and hooked up the wires in reverse. He said once he turned it over he saw smoke coming out of the alternator and then the truck went dead. He cant smell fuel, the engine rotates, there is no spark but all the lights, etc work. What all could he have fried as a result of this, what should we start to look for that might be behind the truck not starting?
Ive searched for this on the forums, but I cant find anything to help, and suggestions?

is there still spark?
reversing the polarity might be worse than you thing on a TPI truck

Hopefully all he took out was a fusable link. If not he could have blown a module.

the truck is a tbi, he said he checked the fuses but did not see anything. what module should we check on?

Is the owner prepared to spend the money it is going to take to repair this?

what module should we check on? Being you said it has no spark, the first one to deal with is the Ignition module in the distributor. Some parts stores where I live, such as NAPA, will test ignition mudules for free. Make sure you use heat sink grease under the module when you install it.

It is possible that a fusible link is burned and no power is getting to the ignition system.

If you find the module is bad, and replacing it gives you spark, the next think to test is:
Does the fuel pump prime (run for a few seconds) when the key is first turn on?
Do the injectors squirt fuel when the engine is cranking?
We are looking for a destroyed ECM here.

I'm assuming you understand the alternator is damaged.