I'm in the process of finalizing installation of a newly rebuilt TH350 (In Lieu of a 200) into a 1965 Cutlass. The rebuild job on the tranny was done over a year ago. During that time, I simply left the tranny in the packaging in order to avoid any dirt contamination etc. The tranny came with a stock tourque coverter already installed. I assumed it already had oil in it but didn't check (hindsights 20-20). My questions are as follows:

1. IF there wasn't any oil in the tourque converter WILL it receive oil from the tranny or do I need to I need to pull it and fill it?
2. When I start the car, put it into gear it pulls the motor down noticably which resulted in turning up the idle. Is this normal (understanding I have a JM 20-22 cam)?
3. The tranny has 6 gears (not sure, but assuming L,2,D,N,R,P) and the cutlass only 5 (L,D,N,R,P). I installed Headers and had to revamp the shifter linkage but since there's only 5 slots on the column will never get it into the lowest gear (assuming this is OK?)

The torque converter distance to the flex plate was good (1/4" or so) but didn't check to be sure the tourque coverter was seated into the tranny properly (it was already installed with a heavy wire holding it in), I've filled the tranny with new fluid (ATF), bent and installed new coolant lines, hooked up the drive line and all accessories, etc. I've put the rear end on stands, started the engine and everything seems to work smoothly so all seems well but have not taken it on the road yet. Just looking for last minute advice so I don't screw anything up and in particular on 3 questions above, Thanks.

 

I assume you mean ST300 (the Junkaway...er, JETaway trans)

Since you've apparently already started the car (see #2 below), the answer is no, you don't need to pull it and fill it. It IS preferable to put some oil in the converter to protect the internal bearings, but the trans oil pump will fill the converter. For future reference, the correct way to start a new trans is to partially fill the oil pan, jack the drive wheels off the ground, then start the engine and cycle the shifter through the gears (stepping on the brake between shifts). As the fluid warms, check the level and top off. This minimizes wear on the internal parts during this initial startup.

Define "noticably". There should be a drop of about 300-400 RPM, maybe a little more due to the cam.

Actually, your new tranny has four gears (3 fwd, 1 rev), the old one had three. Your gear selector has five positions. Yes, you will not be able to get to first manually and that's fine.

On a TH350 or TH400, you should not be able to fit your fingers between the back of the converter and the inside of the bellhousing if the converter is fully seated. Since the oil pump is working, the converter is apparently seated properly.

 

I can't answer your other questions, but as far and the TH-350 having 1 more forward gear than the old 2 speed; that shouldn't be a huge problem.
I replaced the Jetaway (2 speed) in my 67 Cutlass with a TH-350-C. The result is that I can select low gear. The gear indicator on the dashboard just doesn't show it being there. You could always convert it to a floor shift if it really bugs you.