Starts once but not twice after intake gaskets replaced?

Thank you, guys, for your prompt replies.
I should have mentioned that the truck did not have any starting problems prior to gasket replacement. It did have a run ability problem but that was due to the leaking intake and not a starting problem. It is possible the crank sensor failed at the same time as I was replacing the gaskets but seems a bit coincidental. Each time I recheck rotor position after start and fail to start it is at #1 TDC still. I've re stabbed the distributor several times by rotating the engine till it's at TDC then re stab it and it will start. Then shut it down and when I try to restart it the sound is not normal sounds like it's way out of time. The sound it makes is like it grinds and binds up like if the starter is loose almost. But after a few stab it cranks normally and starts. I will check the crank sensor for debris and possibly replace it if there is no other reason for this symptom to be occurring.
One more note about it. Just prior to repair, I drove it approximately 5 miles with no issue. Parked it and after 30 minutes or so went to move the truck and it cranked, started normally but kept stalling when I went to move. Would not stay running once put in gear. I had to neutral drop it to get it to move the several feet needed to get my truck out from behind it. I'm doing this repair on a friend's truck. After a couple minutes it did better but still ran badly due to intake leak or do I assume. After that move I didn't try it again for a few hours. After it say it started and idled good, and I was able to move it to spot I did the repair at. Then after replacing the gaskets it did what my question states.
I'm not a novice or shade tree mechanic. I've had many years as a professional auto technician but changed my career shortly after OBD2 was law. For those who don't know what that means, in 1996 all vehicles were required to have On Board Diagnostics (OBD) in 1996. My last year as an auto tech was 1999. I've dabbled in auto repair for friends and my own vehicles ever since but not professionally. I'm now an RV technician and rarely work on drivetrains. I appreciate this site and the wonderful folks willing to help us.
Please let me know if I'm not supplying any needed info of my situation. And if I and assist in any questions you or your subscribers may have about RVs, I'd be happy to return the favor.

For Ken L. I will see if I can get a video for you if both ways this engine acts, starts cleanly and when it cranks ugly and not start. That will be tomorrow morning as I'm in Alaska and it's 2217hrs at the moment.
But more info on the original repair procedure. I did mark the distributor prior to removal but the engine was so covered in oil and dirt (hence the reason for changing the rocker cover gaskets) during the cleanup my markes were erased so had to go to manual timing procedure of finding TDC compression of #1 cylinder and align rotor to corresponding position of dist cap. Truck fired ran well and test drive of of approx 5 miles went well with no pinging and only slight hesitation but no lack of performance. Turned truck off, no diesel or run-on and would not start acting as if more that 30 degrees out of time. Engine sound while cranking was bad with predetonation and grinding/binding of starter. Best way I can describe the sound. I'll attempt to get video and sound but this phone and Internet isn't that great. Thanks again for your knowledge and time.

You are correct Steve W. That was why I'm at such a loss as to what's going on. It's either good or bad as far as stabbing the distributor, there is no almost or close.
I went back to the truck yesterday after the owner called to say he purchased new keys and while checking if the cuts to the blank keys were good (not a chipped key) he started and shut down the truck for each key and it started each time. I figured if anything it's a heat soak situation. So, I went to it, ran it for 10 minutes (after starting it three times cold.) Shut it down and it started, ran it another 10 minutes and it did fine. So, I let it sit till completely cold, warmed it up as I would any truck and then drove the hell out of it to see if heat or one of the IM readiness parameters had anything to do with it. Restarted fine. Cleared codes to wipe the readiness parameters and it did fine again.
So, it's cured whatever the heck it was is no longer causing an issue. I didn't do anything to the timing or engine at all from the last fail to start and the recent starts that were normal. So sadly, I have no information to share that might help someone else if something like that happens to them. But all is well, and I thank you guys for everything. I'll keep using this site and if I find myself in a similar situation or come across something that may help others, I'll surely post it here. Happy summer everyone.