With regards to T-bolt clamp size requirements, that really depends on how thick or how many plys your hoses have? OEM original hoses were very thin 1 - 1.5 ply designs. 99.99% of folks by now, have upgraded their hoses to the thicker 2 - 4 ply design hoses. This dramatically affects the clamp size needed. Also, the type of hose will alter the requirements as well. Factory style Nomex / Silicone vs Rubber cloth braid re-enforced style.
I can tell you, the T-bolt clamps that we sell are specifically matched to our hoses that we sell as well. We only sell the Nomex/Silicone 4 ply type hoses.
The clamp for our 2" hoses have an adjustment range of 2" to 2.5" ID.
What I personally like to do is, remove the spring, install the clamp and tighten as much as I like. Then mark the excess with a marker and cut the excess stud off with a dremel or wiz wheel cutter. I like to leave about a 1/4" stud protruding past the nut myself. Nothing like getting bit by a t-bolt clamp stud while working on your car. WOOHOO, fun for the whole family right there.
The easy way to do this, would be to take your hose / hoses with you to that store to test fit them. Don't forget to bring along a 7/16" wrench with you just in case those clamps' nuts are snug. Most of the time, that is the nut size.
Hope this helps.
Patrick