ghost: There've been a number of good builds from members who've used the 1601. Just to name three, there's ubiquitous, alligoat, and me. There's some good information in response to my thread here.
Regarding the Tropic 22, it's a much rarer crystal to find in the wild than, say, a T19 or a T21. You could try asking around VRM, but don't be surprised at paying at least $150 for a service crystal, and at least $250 for an older, domed T22. Also, posting a WTB over there is fraught with risk, so make sure you know the seller.
As far as aftermarket options go, automatico turned me onto the GS Tropic 22. If you can find one, I recommend it over the Clark T22.