V belt issues and install

[SeeTen]

Hey all! My brother and I are working on a '69 C10 with a Factory Crate 307. (Pictures coming soon, but I haven't found the time... too much to do). To date, we've done full suspension (PO thought it would be a good idea to heat the springs. The 40 YEAR OLD springs), a few other random things, and most recently the intake manifold and carb (to get rid of that clogged 'ol 2bbl).

In doing the carb install, found that it was easier it slide the alternator down the bracket to get the valve covers back on, and decided a change of the belt was in order.

It looks like the current setup runs not only the alternator, but the W/P as well (one big belt). I've tried looking up diagrams, advice whether this is OK or not, all to no avail. It was my understanding that since I have a two-groove crank and W/P that I should have a separate belt spanning that distance - and then the alternator as well.

Trouble is - can't find a size for this W/P to Crank belt, nor (as embarrassing as it is to admit it) any info on how to get it over the water pump and crank pulley. Are there any adjusting bolts on either to release tension? I know I'm not meant to pry it over the grooves (once I do find a belt to fit) but I can't figure any other way to get it on while retaining proper tension.

In short, need to know how my V-belt(s) should be set up w/ only an alternator and water pump, on a two-groove crank and w/p pulley system.

No A/C or P/S, so it shouldn't be this hard...

Thanks guys!