People gravitate to 700C for the wider tire selection.
27" was the 'old school' trend of a touring wheel.
If you need to replace parts, might as well go 700C.
Nice find, especially if it's your size. The shifters were the original Gripshift road shifters. Are they 7 speed index?
I found the sister bike to your Miyata, a Specialized Expedition a few years ago for a great price, but it's 1 size too big.
I assume 8 speed index or more. It can handle all positions of the 8 speed cluster. It's not dialed in very well as is. Yeah I'm thinking I'll take the slower route of getting it just the way I want, rather than getting it rolling as quickly as possible. It'll take me awhile to chip away at it. The eight speed cluster is somewhat of an issue anyway as the 11T, 13T, and maybe 15T drop too low for chain stay loop when in the 3rd ring. The catalog listed a 5 speed cluster. It went down to 14T, but the 3rd chain ring was a 28T; mine is 24T. Maybe just enough of offset to keep the 14T above the chain stay loop.