If I decide I want to put a different engine in my half ton suburban I want to replace my GM goodwrench with a J model. What is the quickest and easiest way to determine what model I'm looking at? Also, any years I should steer clear of?

Well quickest and easiest to see if its a C or J code engine, to me, is to take the airfilter cleaner top off and look for a EGR. C's had them, J's didnt.

As far as I know, the only differences between the two was the EGR and the different injector pumps.

Blocks are all the same, head configureations varied from year to year. J's had bigger valves in early years. Later years it is a toss up. Goodwrench engines only came in one variation, no difference c or j.

So, does a goodwrench have EGR or not? What was different about the injector pumps? Is the EGR that thing in the center of the intake manifold with the vacuum lines connected to it? What happens if you diconnect the line(s)?

The egr system is totally contained in the intake manifold, gases are routed from an exhaust port on the head to the egr valve and into the intake when prompted. Result is loss of power and sooted up messy intake runners and intake valves.

To change to a non egr system, the best is to find a J intake manifold and buy a set of J intake gaskets,(they have stainless plugs to block off the exhaust port on the heads). The J manifold flows a lot more air because it doen't have that big bulge in the center of the manifold. You can also unbolt the egr valve and make a plate to cover up the hole, this won't help to increase the air flow however. If you watch ebay J manifolds are often for sale cheap. All you need to look for is a open center section(different than yours) there are several different designs, some have dividers and some don't.

As for injection pumps, it is not a big deal unless you are turboing, the fuel flow valve on the c engines doesn't allow as much fuel to flow as the j version does. It flows plenty for a stock engine however.:cool2:

What happens if you disconnect the lines from the egr?

It will fail in the closed position= good. It takes vacuum to open the egr valve. Plug the vacuum line or eliminate the hole egr vacuum circuit so that you don't loose vacuum to your accessories.;)