Varsity Fixie Question

So I picked up an old '72 schwinn varsity off craigslist that was already converted to a fixie. The problem with it is that it has a one piece crank that is heavy as ****. So I bought an adapter to convert it to a 3 piece.seen here (Truvativ American to Euro BB-shell conversion kit, black)
What I want to know is what size hub do I need to get, and what size cranks are most of you using?

You want an English threaded BB for a 68mm wide BB shell ...

The spindle length depends on the crank & spindle type.

Use the double crank of your choice which MATCHES the BB-type, or vice versa.

Of course, you will use only ONE chainring which you will probably need to mount on the inner shoulder to achieve the proper/(better) chainline.

The rear spacing on your frame is probably ~118mm-to~120mm ...

You can use almost ANY older hub that uses a Freewheel ...

Since most will be 126mm wide, you'll want to remove the wide spacer that is on the drive side (which is meant to accommodate a multi-speed Freewheel) and you MAY need to put a thin spacer/washer on the non-drive side ... the object is to center the flanges (some CANNOT be centered).

If, for some reason, you want to use a FLIP-FLOP hub then you will need to respace the frame's rear triangle to the appropriate width -- i.e., whatever the hub "size" is.

FWIW. I chose to respace a 126mm frame down to 120mm ... and, I mounted the chainring on the inner shoulder.

You can certainly respace the frame up to 135mm if you that's the width of the hub you end up with -- that is, you can either fit the hub to the frame OR adjust the frame to fit the hub.

BTW. This is after-the-fact, but you could have simply replaced the original chainring with an alloy, BMX spider + alloy chainring.

I use 165mm cranks on my fixie, although I'd rather have 170mm, same as my track bike. I have plenty of ground clearance, and haven't touched a pedal down in years (except when I've been falling anyway).