Unless it's a Mk1 HW77 action.
The Lug which secures the "anti-bear trap" mech and accepts the forward trigger guard stock bolt is a different OD, on 97s it's 15mm OD whilst early 77s without the ABT are slimmer.
Easiest solution if fitting a Mk1 action into a new stock is to replace the lug (Chambers part #B1332
), and check that the lower sear doesn't foul the stock, a minor mod of the inletting can resolve that. HTH