Stalling when in gear and lurching.

Hi all,

First post here, I'm hoping I can get some answers on about my new ride, and get it back on the road asap with you guys help. I did my best to use the search function to find my problems but just couldn't seem to find anyone with my exact problems.

Here's some back ground, I bought this beautiful red 74 Duster, no rust, nice interior about 3 weeks ago. Apparently rebuilt 318, with no receipts. Only thing was that first and third gear slipped pretty bad in the old 727. So I bought a new 727 from a fella down in San Jose who was a Chrysler transmission tech for 30 years, converter and all. I had my mechanics put the transmission in and ever since I've had this problem.

When the car first starts cold it sounds great, idles great, drives great, flies no problems. In gear and out it idles as it should.

But after a while of driving (about an hour or two of warming up), when I come to a stop at a red light after about 30 seconds, it will idle low, and stall if left alone, and ever so often it'll lurch forward just a bit, foot on the break. If I switch it to neutral it will run fine. I put it into drive and go.

If I let it cool down over night, it runs great in the morning, until it gets warm warm.

I brought it to my mechanics today and they turned up the idle and said try driving it now, although it helped, it ran great until it fully warmed up, then same stuff.

My mechanics also mentioned that my break vacuum booster isn't functioning properly and may be causing this issue as vacuum is escaping when I break, thus the transmission issues. I don't know much about how vacuum works or the inter workings of this car, I have't had time to work on projects much lately.

As a side note, I checked the trans fluid, it's a little high, but no discoloration, no burned smell.

I hope this all makes sense, I've tried to be as clear as possible. Just looking for any advice, avenues to take.

Thanks so much for your time guys.