Well, you didn't mention which model Henry rifle - other than "youth", and I'm not familiar with the particular model - there's Henry rifles, and then there's Henry rifles.
If you're talking about one of the brassies, I don't know what to tell you, since they use a barrel-mounted scope mount ILO receiver grooves & I've never seen how the "BrassLite" takes to D/T for a Winchster 94 type side peep.
If you're talking one of the blued Henry's with the scope-grooved receiver cover, then Williams makes several Models, in two heights, two with Target knobs - that clip into the scope mount grooves. If you go with any of their high line-of-sight models, then a higher front sight is also gonna be needed to zero the rifle.
They are the: 5D-AG, 5D-GR, FP-AG, and FP-AG-TK. The 5D peeps cost about half of the FoolProofs, but they don't have the click adjustments,either.
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JMO, But I think the Brassie's cantilever scope mount would put any of these peep too high for any but a custom front sight -
very high.
A tang sight could aways be mounted, if it's a Brassie.