Cheapest Way to 180mm Cranks
I've been building up an old Trek 930 steel frame from 1991 on the cheap -- looks pretty cool in black with neon green letters (ah, those were styles back then, eh? But I digress)... I'm a tall guy and I have often felt under-torqued on hills in the past. I want to try out a crank length over 175mm and 180mm seems the most common of those uncommon sizes. What's the cheapest way to get there?
Option 1) I have both a compact triple outer set of chainrings (94 bcd), and a standard "touring" triple outer set (110 bcd). Is there a cheap 180mm+ crank I can just bolt right in the middle of one of those sets? How much? Who makes it?
Option 2) I've also read here about putting on BMX cranks (which are often 180mm and over, and as cheap as $20 used) and I think my 68mm B.B. shell will accept a certain kind of BMX B.B., right? But I'm unclear about how to correctly convert and line-up the chainrings.
Option 3) Or I could just run a single speed in the front, skip the chainrings (and scrap my antique derailleur), find a used Surly, XT or whatever crank with teeth in the 30s (which show up for over $100 sometimes, used) and hope to hell my legs can handle the hills in San Francisco!
If it matters, I have a 7 and an 8-speed rear cassette to choose from in all this. I'm unclear how concerned I need to be about chain allignment there.