Transmission swap out issues; Please help!!!!!!!
 

I have an '81 chevy long bed pick up in which the tranny went out. Bad tranny, 700R4; replacment tranny, Hydramatic 400. Completed the conversions; Drive shaft, slip yoke, mounting bracket. Drove great the first day, then on third, truck began whirring/whining while in drive and also I lost gears. Looked up info on web/here and found suggestions. 1st mistake was the I didn't make sure the clearance of the torque converter was correct. Well, that has been done, but whirring/whining stopped momentarily, then started back up, but now in all gears and worse when gave it gas. Info pointed to next issue, no fluid being circulated. Should have done this in beginning but once again, trial and error, drained fluid and changed the filter. Whirring/whining has stopped, now my drive is only shifting in high accelerration, and not even into third. Manually, I can shift, but very ugly and third is hesitant. Today, I replaced the Vacuum modeulator and noticed a moderate difference, but it feels like a slight slippage when starting in first gear, but it isn't slipping; and it just does not FEEL like it's back to it's old self, you know what I mean? Help is appreciated, as this was my first time doing this. Thanks.