Hello: new to this forum so hello to all. The problem the when the gas is hit hard the engines revs but the truck does not move at speed that matches rev's, something slipping. Where do I start, I have just put in new clutch and bell with no help. Thanks ahead of time for all help.

Since you've you've just put in a new clutch and bell, make sure the actual installation was done correctly. If you didn't have this problem before you replaced these parts, then that's most probably where your issue is.

Next up if you've already tried this - check if the screws holding the outdrive cups from the diffs are still in and tightened - these can come loose. Tighten them down and remember to use locktite on all screws going into metal. Next up is checking if your diffs are finished...

Let us know what you ended up having to fix/tighten.