I've owned a Spit6. It's kinda fun in an occasional sort of way. Those extra 2 cylinders hanging over the front axle really DO mess up the handling. My GT6 and normal '79 Spit are more fun.
What the OP car had going for it was the O/D trans. Hard to say if the asking price was good or not without seeing it in person. The lack of info in the listing makes it seem on the high side. FWIW, I sold my Spit6 4 years ago in good running condition (also with O/D) and a GT6 front brake conversion for about $5K.
Datsun1500 wrote: Compare it to this one posted on this forum last year. http://grassrootsmotorsports.com/forum/open-classifieds/1979-triumph-spitfire-1500-jackson-michigan/67131/page1/
I'm the one who eventually did buy this car. 
