As long as you don't plan to add an optic, I'd recommend a Williams WGRS sight.

It'll mount on th receiver, using the holes already drilled and tapped for scopes.

Williams WGRS-336 Guide Receiver Peep Sight Marlin 336 Lever Action Aluminum Black - MidwayUSA

Cheaper at Brownells, if you have an account:

"WGRS" RECEIVER SIGHTS - Brownells