Shifting too far in 3rd gear....?

You have a few things to check.
One thing that can happen is the ramp or taper that the brass ring rides on can wear.
Also the brass ring can wear.
You check them with the gear out and you push the ring down and make sure it stops spinning.
If it doesn't stop turning the trans gear will never sync and line up.
I had this problem in a 3.09 gear set with second gear.
Drive it normal, no problem.
Add high RPM and it would not shift into gear.

Again thank you to all,I will be bringing it in the end of the month as we here in Canada don't have the great weather you guys have in a lot of States that you can run the cars more or less almost all yr.
We start around April (if we are lucky) but by May we are out but by Halloween it's the last day. We lock them up. No treats, no tricks.
Now the "vintage" (Harley Davidson 440) snowmobile starts getting ready to come out.
Oh well, as can't have it all..lol
Thanks Gents.
MAPS