TJ,
As far as I know, the G37s had solid sides and laminated arched back (both in maple). Early G-37s (like my '74) had one piece mahogany necks and silk-screened GUILD on the headstock. Later G-37s had multi-piece (3 and/or 5-piece?) maple/mahogany/maple necks with the Chesterfield on the headstock (and from the examples I have seen, tended to have a bit more figure in the wood). The D-30 was similar to late G-37s, which it essentially replaced, being introduced the year after discontinuation of the G-37. The only real spec difference I saw in Beesley's description was scalloped bracing on the D-30, and the "new" tapered headstock design. Can't vouch for that, since I have'nt seen one in person.
I love my old G-37... has a very balanced, smooth, mellow tone. Mine isn't the loudest of my dreads... tho' others have commented on the volume and projection of their G-37s (most of these have been newer, with the maple laminated neck... I have speculated that the stiffer neck may transfer more energy/vibration to the body?).
Dave
