How much would it cost to buy a surplus Cessna T-37?

Question

Also would it be possible to put more efficient turbines in it?

Answer 1

Well, the A-37 had the GE J-85s which were much better than the J-69s although not what I would call efficient.  I saw one at the War Crimes museum in Ho Chi Minh City, maybe they will sell it to you.

Answer 2

There is an A-37 Dragonfly (the attack version) for sale at Courtesy Aircraft for $695,000.  Click on "Inventory".   I'm sure you can upgrade the engines as it is probably licensed as "experimental /exhibition".  Finding an A&P to do the upgrade may be difficult.  I've seen T-37's for sale for a little less on ebay and other aircraft websites.  

Hope this helps...