1. Uses a copal 0
3. Rear filter thread of under 62mm
For these 2 criteria, you can look
here, all the newest lenses listed with shutter and filter sizes (and all Fujinons are
here). There's a list of older lenses
here but no shutter sizes listed.
Apo Sironar N/S (inc Caltar II-N), Nikkor & Fujinon W, Apo-symmar, G-Claron and Xenar, they all have <62mm fronts (The Fujinon CM-W has 67mm front so might be <62mm rear, not sure).
Out of all of them, the G-Clarons and Xenars are the cheapest, but you'll get less coverage. A regular Symmar-S or even original convertible Symmar shouldn't be over $150-200, if you're lucky you could get a bargain Apo-Symmar for $300 (but then, I'm looking at fleabay prices).
As for length, that's really up to you. I've only got 90mm and 180mm, I'm still deciding myself whether to get a 135 in the middle or get a 150 and sell the 180. Depends on what this 'new project' is that warrants the focal length.