1964 K10 Carry-All/ Suburban

[DBear]

Howdy,
New to the 60-66 Suburban's, and looking pull the trigger on a 1964 K10 Suburban. I have and had a few of the 67-72 3 door suburban's, but not very knowledgeable on these years. What I do know about this 1964 Burb; it is a K10, straight 6, manual transmission. The transmission is on the floor, for the steering column is a floor shift model. After looking thru the GM Heritage Center vehicle info kits, seems that is has 2 different trans options, a 3 speed, and a GM 4 speed. With this being a floor shift model, does that mean it's a 4 speed variety? Seats are in it, but only frames (front seats). Rear seat looks like a 67-72 K5 rear seat. It is a barn door version. Seems complete, other than the correct rear seat, and very solid. What do you guys think? Thank you for your time.