Very nice group you have there. I do like the large levers also, I added an SBL lever to my 444XLR. It made it almost perfect, just needs a full length magazine tube now.
My Next project is to build the Stainless Guide into a SBL look alike.
KEN TN -> Nice group of Marlins! That sound like a good plan on the Guide Gun, I like the straight stocks, but the pistol grip and big loops have been growing on me! Good luck with your project and don't forget to give us pics!