victory is close, I can smell it......

My neighbor and I have dropped a new motor in his '88 c1500. There are basically three heads that have been working on this from start to the all so very close finish. Between the three of us, our mechanical apptitude is very strong and I can honestly say we heva all checked over each others work. Not because we didn't trust what the other did, but just to keep ourselves in check.
With all this said, we breifly tried to fire it up today but there is a small issue to figure out. We stopped while we were ahead to rest, and regroup with our heads clear. So, I'm looking for some advice from some of you pro's who just might know....
Basically, upon turning the key, something ain't sounding exactly right, however, it does not sound bad. Kinda sounds like possibly the starter not shimmed right, like as if the starter was binding against the flywheel but this isn't the problem as we did not use any shims and the motor is turning. That is just what it sounds like in a way. One thing we are leaning towrds being the problem is somewhere, somehow, something with the distributor isn't 100% (besides being timed). At one point it did backfire back through the throttle body. We know this is probably simply a timing issue that can be dealt with when we get it to fire up. But for some reason it sounds like it ain't ready to fire. Battery should have the juice needed to crank it, we are getting fuel just fine, I hear the coil sparking, plug wires confirmed to be wired to the cap properly 3 times, new cap/rotor. It definantly seems to be with the distributor. But I can't figure out why it sounds the it sounds.
As I mentioned, we only briefly tried to crank it up, but stopped immediatley when we realized how far ahead we were and how close we are. so, any ideas/suggestions from those who may know would be greatly appreciated.

Oh yeah, this is a 5.7L motor we are putting in (same as it was) just in case anyone was wondering before they had some advice. Don't think it would really change the senario but hey....

Sounds like you need to verify that distributer is in correct position. Backfire is caused in this case by plug firing when exhaust valve is open. You are probably 180 degrees off. If you don't want to pull dist. to check you can switch wires 180 degrees on dist cap. Or you could have wires on in mixed up firing order--this causes strange sounding cranking. Check wires first, then check dist position.

I agree w mbumgua . Also make sure you have the correct flex plate to!Remember top dead center on #1 piston & on #1 in the cap!

A incorrectly timmed engine can make the cranking fase of the engine sound really wierd. Make sure the timming is right!