Transmission Inquiry

[jokers_vs_clowns]

I love old trucks but I am no mechanic. I know I have a minor transmission leak. Liquid is red and its on on/around the transmission. I checked the level of fluid and it say "add 1 PT" (yes the truck was hot and I went through all the gears while having the E-brake on) I practically added the entire Quart of tranny fluid and the level hasn't changed. It barely shifts hard from first to second but unnoticable from second to third. I have no idea if its the original tranny or the original dip stick. Is there another way I can check the fluid level without trying to figure out if the tranny is original and the dipstick was replaced or the other way around???
Engine is a 350 small block with a 400h tranny. At least that's what the guy said who sold it to me. Any tips/tricks/advice is appreciated.