I run a Skinner barrel mounted peep on my 60 and like it very much. Not as nice as a receiver mount but a big improvement over the stock notch. You can read my review of this sight here: http://www.marlinowners.com/forums/index.php/topic,78733.0.html
On my 795 I run Tech Sights and they are excellent. It is a rear and front replacement. They now have the option of swapping apertures too and that is a big plus (wasn't available when I bought mine). They are somewhat expensive but I think well worth the money. A bit of a pain to adjust elevation (nothing difficult just tedious). Definitely get the adjustment tool on their options page, it really helps with this. They are very well made and stay put on the dovetail ramp. I need to do a review of them as well.
Another option is the Marbles Bullseye. It too is a barrel mount and pretty inexpensive. I prefer the Skinner.
I do think Williams sells sights that will fit. You have to look for dovetail ramp mount or some such. I could be wrong but I thought I'd seen them.
Any specific questions, let me know.
On my 795 I run Tech Sights and they are excellent. It is a rear and front replacement. They now have the option of swapping apertures too and that is a big plus (wasn't available when I bought mine). They are somewhat expensive but I think well worth the money. A bit of a pain to adjust elevation (nothing difficult just tedious). Definitely get the adjustment tool on their options page, it really helps with this. They are very well made and stay put on the dovetail ramp. I need to do a review of them as well.
Another option is the Marbles Bullseye. It too is a barrel mount and pretty inexpensive. I prefer the Skinner.
I do think Williams sells sights that will fit. You have to look for dovetail ramp mount or some such. I could be wrong but I thought I'd seen them.
Any specific questions, let me know.