Wild West Guns have the Wild West Marlin trigger happy kit. I installed one on my 336 - 35 Remington and it worked great. It brought it down to about 3.25 lbs. I'm not sure if they have them for the 308. You can check directly with them or at midwayusa.com, cabelas.com and even gunbroker. I don't know about the head space gauge. Good luck.