73 Manual trans

There was the standard 3-speed and the optional toploader 4-speed. Probably all the 4-speeds were wide ratio - I don't think the close ratio was available any more in 73. If I were starting from scratch like you are, I would just go ahead and put a 5-speed in it. That way you can run steeper rear gears (which 4V Clevelands need) and still cruise on the highway.

If your cleveland is stock the T-5 is an acceptable option. However, if your Cleveland is built and you plan on driving hard you'll want to think twice about using a T5 (max torque rating is 300lbs.) and think about a Tremec TKO. It's a bit pricier but it was engineered to handle the amount of torque a healthy Cleveland produces.
A true bolt in will be a toploader. I did the exact same conversion you're thinking of 2 years ago. The hardest part is finding the clutch linkage and pedals.