I did some work to my Guide Gun, added a Williams FP, a sight blank, a steel magazine follower, and a happy trigger.
The FP336 was simple, uses the rear two scope mounting holes. On my GS, the screw in aperture overhangs the hammer slightly, you can still cock, decock safely, but its there. I don't believe its an issue on the sights that mount to the side of the reciever. Do yourself a favor if you mount an FP, screw the locking screws in and out about 3 turns a couple of times before you loosen them 1/2 turn to adjust the sight, there must have been some residue in mine. With the sight mounted I can see how asymetrical my front ramp is.
I didn't have a brass drift/punch to remove the sight and install the blank, so I used a 270 case. I thought the sight would take a lot more effort to move, one good whack and I am on my hands and knees across the room for 5 minutes looking for the sight. The blank didn't go in as easily. Before I broke out my miniature files I had shortened the 270 case to about 1 inch. Looks good now, a little No9 and fine steel wool take the brass marks right off.
I installed a stainless steel magazine follower from DRC, its a beauty, too bad you can't see it in the gun. I know it will last forever, I had my doubts about the plastic factory plug.
Last thing I did was install a Happy Trigger from WWG, its well named. The trigger dropped right in, its actually easier to assemble with the WWG trigger and the pull is much improved. Marlin flop is history, if that bothers you. Test the trigger before you re-install the mainspring (I had to temp install my lever to push in the little stud so I could pull the trigger, I didn't have enough fingers to do it without the lever.
Now I can't wait to take my sons to the range Saturday.
Andy

Andy,

Good info; thanks. I have one question to ALL who have installed the WWG Happy Trigger on their Marlins: Is anyone unHappy?

I am going to install this trigger on my Marlin "shooters" in 45-70 Gov't, 44 Mag, 375 Win, 35 Rem, 30-30 Win, and 25-20 Win. In total, it's a sizable investment and I just want to be certain that there's not going to be any pitfalls.

I've installed over a dozen Happy triggers, and, like you said, it's a sizable investment but I'm happy I swapped them out. Not all the rifles needed it, but now all my Marlin triggers feel consistent and clean. It's arguably the best aftermarket upgrade that you can add.

I couldn't believe the difference when I installed it. If I was in your shoes, I would buy one for the worst triggered gun and see how it works before I bought one for every rifle.
Andy

Figure what you want o. If you haven't tried one and you don't like the factory trigger install the Happy Trigger kit and the Bearproof Ejector. They ARE pricey but if you like a "crisp" no-wiggle trigger on your lever guns then do it. Don't wait and listen to the advice of people who have never used one. I have both items and will install a set on each new Marlin lever gun I own. Good luck. Bandito