Linton is the only place that runs non-wing upright 600's.
The MMSA and AMSA are organizations for upright winged mini sprint racing. MMSA rules say stock bore and stroke 1000cc or less only. AMSA lets you run as high as 1200cc +/-
I recently filmed the MMSA at two tracks. One was the Bartholomew County Fairgrounds in Columbus, IN and Bloomington Speedway in Bloomington, IN. My advice to anyone looking to get into mini sprints is to go to a race. Go in the pits, talk to drivers and their crews. Most drivers will answer all your questions.
I personally ran an upright 600cc @ Salem and with the MMSA and AMSA at Twin Cities. I ran an ERC chassis with a Kawasaki 636. I was told that the 636 was the BEST 600cc engine you could use. I may have heard wrong, but more than one person told me that. If you run with the MMSA there is bonus money available for the highest finishing 600cc car. And if you run a smaller track with the MMSA or AMSA...a 600cc really isnt going to be that bad, and you could do quite well.
To the best of my knowledge...MMSA pays $1000 to win ($600 for non members) and AMSA pays $500 to win. $100 to start for MMSA and $50 to start for AMSA.
If you had an upright mini sprint this year...you could run at these tracks....
Lawrenceburg
Bloomington
Columbus Fairgrounds
Brownstown
Kokomo
Gas City
Linton
Salem
Twin Cities
Moler Raceway

There may be more...but those are what I can think of off the top of my head. Mini sprints are a great way to get out on the track. I wish the drivers and the organizations the best.

Check out my website to purchase DVDs of Mini's and Sprint cars! www.cmiracingvids.com