Factory loads for 45-70 can be pretty light to begin with. And it is one of the best cartridges for reloading. I was going to buy a guide gun. I've played around with them quite a bit but never shot one and the only reason I didn't buy one is because I want to buy the 1895cb instead and have it shrunk down to 22" so it will have greater capacity than the guide gun.
I have the 1895 GS in .45/70. I LOVE it. It is my go-to hunting gun. You can get some SAAMI spec Remington 405 GR. that are downright pleasant to shoot. I also uploaded some 550 Gr. Mt Baldy thumpers to 1600 FPS that I thought were going to knock me down. It is a wonderful and versatile rifle for hunting, as long as the game is less than 150 yards. For detail work, I prefer the 7mm Mag.
I have a stainless guide gun that I keep on my boat. I have the full-size 95 at home. The guide gun is my favorite rifle. The only load I use is a 405gr cast bullet and 52 grains of 3031. Does about 1550fps and is amazingly accurate out to 100 yards. Have shot groups with this load (scoped for testing) at 100 yards that hovered around one inch for 5 shots. All groups under 2". I happen to like iron sights, and so use the gun with peep and a post. Can still make 4" groups at 100 with the irons. Can't say enough good things about the Marlin guide gun.