My .02 and about what my take is worth, but here it is. To me, the 72 and earlier Westerly Guild hits the sweet spot of not having the Hoboken premium cost, but still having the light build. This comes with the light build propensity of needing the major work. Heavier builds are less likely to need it, but still, you have a forty year old guitar, so there you go.
The work an older guitar will need is likely to exceed post work value. If that D 40 is $500, I'd buy it if it was 70 or 72 vintage. This is personal to me and hopefully you will get opposite opinions on this. Either way, a thousand will be spent. I had to source a new bridge, but one can be made. I would never get a neck reset without a fret job too. This may need a new nut too. Work is not going to be done in a week or two, so you'll likely be without the guitar for a while. How long a back up a tech has is usually a sign of how good they are. An old guitar is rarely a bargain, but rather a state of mind, for their worth is in the aged wood, an impossible to monetize trait.
Modern guitars are generally well made, and you might be the sort that would be happier with a New Hartford era guitar. Only you can say. I remember when I bought my D 35 twenty five years ago, Richard of Gryphon said, remember, you aren't buying this to save money. At $250, it would not have made sense for them to do the work on a guitar they would sell for $800. Ten years later, I spent $1100 more on the guitar. Ten years later I could get my money back. I've never regretted bringing a US made solid wood guitar back to life. I'd sell my Martin D 35 custom and my 65 Texan before I'd sell the 70 D 35 Guild. The Santa Cruz wins for now.
Now we still live in an age Guilds are undervalued. For $1500 or less you can buy an old 50 year old guitar and fix it. Try finding a 70 D 18 you would not have to spend $3000 for. That or more is what a shop around here with a good repair department would charge for one ready to go. I'm not saying it's not worth it.
