Another possibility for tenor necks: Wyatt Fawley makes five string necks and replaces tenor necks with them: he might be a good source (of course, he'd make you a tenor neck for a very reasonable price). I don't remember his URL but it's available from Michael Holmes at www.mugwumps.com--from whom I bought a banjo with a neck by Fawley).

And jO, I have a Martin guitar I'd be glad to trade for your Vega, but you'd probably want another thousand bucks or so on top of that (mine is a 2 year old D-1). But my Wildwood Minstrel TuBaPhone is sulking in the livingroom, so I'd better stop thinking about it (she hates my drool falling on her face). --seed