If you're going to be easy on the car, I would suggest a World Class T5. They're rated for about 400hp. First gear on those are 2.95:1, roughly the same as a TKO 600 or wide ratio Toploader.
If you're dead set on a lower 1st gear, you can opt with a TKO 500, with a 3.27:1 1st gear.
However, I don't think you need anything that low...and any engine with any torque at all should be able to move a 2500 lb car (on a hill or otherwise) with a super low 1st gear. If 5th gear is too high for you in a 55-60mph zone, then just use 4th gear.
If I were in your spot, just wanting a cruiser, I'd go with a new T5.
I sell all of the above and can help you fine tune a decision.
Shoot me an email,
brent@b2motorsportsllc.com or give me a call: 502.759.1431