Anything 6" or over is fine. My SBH is 10-1/2", left over from IHMSA. Deadly accurate.
Going shorter then 6" and you might have trouble making heavy boolits stable because of velocity loss. Sure some say it is little but a little goes a long way when trying to spin up boolits. I would say 7-1/2" to 10" would be my choice.
Henry Ford said you could buy a car in any color---as long as it was BLACK!

I owned a lot of Fords and back then "found on road dead" or "fix or repair daily" was 100% correct. Had a lot of trouble with GM's too. I worked for a Desoto, Plymouth dealership and would never buy one either. Power up the ying yang but a steady line into maintenance. I would spend all day on the road starting the dumb things when it was cold out.
I remember the push button shift, step on the gas and WOW, 100 mph right now. Then the 57 Chevy with fuel injection--a rocket!