Recently I picked up a waffle top 336A in .35 Rem. I would like to find a steel Lyman receiver sight for it. Is a 66LA the proper sight? If so, where can I find one?

Yes. I found one for my 336A on eBay.

What year is your 336? If you're looking to match the vintage of your rifle it would be either a 56LA or a 66LA. The 66 series was introduced in 1955, the 56 was made from the '30s till late '50s. I have a 56LA I was going to mount on my 1936SC but I'm reluctant to D&T it. I'm hoping to find a nice waffle top 336SC someday to use it on.

66A left, 56LA right

Thanks!