Built351Cleaver

Last year I had a B&M Megashifter installed in my 68 with a 351C and fully manual valve body C6 trans. Now it's really been nothing but problems to shift this beast since I got it a few years ago. I had a Hurst ratchet shifter in at first, with the same problem as I have now of not being able to shift into first gear until the tranny warms up a bit.
But also now with this Megashifter, I can sit with the car off and my foot on the brake and shift from Park to R to N to 321 and back up to park and every movement of the handle feels solid and firm, like its been ratcheted into the exact correct position. But after I turn the engine over and the car is sitting in idle, I can NEVER shift all the way into first when the car is room temp and hasn't been driven and warmed up. It almost feels like theres something in the way at the bottom of the shifter, if that makes sense.
Not to mention that when I'm in 3rd, displays that I'm in neutral, and I lose control of neutral completely the more I shift and drive. I'm not sure if theres some kind of vacuum I'm missing or a cable that isn't hooked up but I don't know how to fix it. Thanks for any help guys