I've been looking at options for a sub-40" rifle as a modern "truck gun", the current nominee for that duty is a Stevens 325-A which has remained un-scoped and will remain so.
I generally dislike the Accutrigger and whatever Ruger calls their variant, but both they and Savage have some neat stuff in that size. Generally, to hit my "perfect ten" it would need to be 20" in a short-action cartridge. For a .243 I would prefer Ruger or Remington for the faster twist barrel. 6mm/6.5mm Creedmoor both good. .260/7mm-08 also fine, but .308 Win probably about perfect. Stock-wise I probably could get away with regular LOP/recoil pad but a youth size would be nice as well, my boy likes to shoot but he's still pretty small, just over 5 foot and a buck twenty at 13.
A good old fashioned Remington m700 short action would be about perfect, 20" sporter barrel, .308 with AICS-compatible bottom metal and a Triggertech Primary. LPVO in a 0 MOA rail. Threaded is a bonus but I don't much care. The Vanguard Compact also crossed my mind, I have a regular Vanguard I'm fond of and taking 4 inches off the barrel and another inch off the stock plus it being a short action would get into the right size category, and Legacy has DBM kits for them as well.
Or, as stated, just chop down a T3x - ATRS would make quick and fine work of that and they could send it back with a rail and set of their rings, too.