I Just Replaced My 327 With A 350 . After Connecting Every I Started The Car And It Was Stuck In Third Gear Is Anyone Who Can Tell How To Correct This Problem

Sounds like a shifter linkage issue to me. What trans, what shifter, which linkage do you have? Did you disconnect any of the linkage and maybe put something on backwards?

More details and a photo of your linkage would be good.

The shifter's not adjusted properly, the lever's in third but the 1-2 link is still in second. Go underneath, flip both linkages into neutral, then put a 1/4" drillbit thru the holes in the hurst shifter and adjust the links so all the holes line up

I've had 4 of them stick in third gear. If moving the linkage dosen't fix it, it's likely that the syncronizer struts have come out (usually due to a failure of the retaining spring) and wedged between the syncro and slider, locking the trans in third. I don't know why it's always third though. I've ever been lucky enough to just be a linkage issue.