Most of the questions you are asking have to be answered in a context. You tell us you want to use it to cruise, not hot rodding or racing. Not racing I understand, the difference between hot rodding and cruising I don't understand, though knowing probably would not change my response.

If by crusing you mean going slow like often happens at a car show you definitely want an automatic transmission. With 3.08 grears my car with a T-10 4-speed goes 5 mph at an idle. Your speed at idle will depend on the height of your tires, your gear ratio and your idle speed. Each of these factors mean other choices.

If cruising is a pleasant mixed highway and surface street trip to someplace where you park the car and talk, then the choices might be different. In that environment my 4-speed car with 3.08 gears is perfect.

My '55 1st GMC has 3.08 gears, a 270 GMC six and a granny gear type 4-speed. Sometimes it makes sense sometimes it doesn't.

I would encourage you to think through what's most important to you and then work from there. If you have a look you are after or a list of driving situations you care about, it will be easier to make these choices.

1955 1st GMC Suburban | 1954 GMC 250 trailer puller project | 1954 GMC 250 Hydra-Matic | 1954 Chevy 3100 . 1947 Chevy COE | and more...
It's true. I really don't do anything but browse the Internet looking for trouble...