I have an 1990 Trek 700 Multitrack (the difference between the 700 and 730 as I understand it is that your main tubes are butted and you have a chrome-moly fork) that is set up as a light touring bike. I love the frameset and find it very comfortable to ride having done several centuries, some group rides, and lots of training on it. I have upgraded it to all Deore and Deore LX, Specialized Avatar endurance seat, Ergon GC2 grips, and handbuilt 36-spoke touring wheelset. I had a discussion with a shop owner about "upgrading" to a CrossCheck or LHT frameset but when I looked at the specs, the LHT frameset was just a half pound lighter than my 700 frameset and I could gain half of that back just by switching to a chrome-moly fork. The CrossCheck was about a pound lighter and had a more aggressive geometry. Both the LHT and the CrossCheck are excellent framesets and would be entirely appropriate as bikes for recreation, fitness, and centuries, but I decided the small weight savings wasn't worth it for me. I am still carrying an excess 30+ pounds of bodyweight and it seemed foolish to put $500 into switching framesets for a pound or less of weight savings on a bike set up for touring and non-competitive charity rides.
With butted tubes and a chrome-moly fork, I'd be willing to bet that your frameset isn't significantly heavier than an LHT and only slightly heavier than a CrossCheck. The 700 series Treks are well known for durability and comfort so if you decide to go with a CrossCheck frame, contact me and I'll gladly take that 21" 730 frameset off your hands.