Unless you are willing to spend a ton of $$ and/or a ton of time finding a gem, a Springfield standard M1A plus a USGI extractor for $12.00 (PS15SAPW) and spring and plunger for $5.00 (PS1617SAPW) from CMP is the most straight forward way to give your dad what he wants. No, it won't have a bayonet lug but does he really want one? I doubt it, I didn't, however, if you do they are available but you'll need to also get a special wrench to get the nut off that holds it on.
Get him the standard one rather than a scout squad or shortened one because that's what he trained with in the Army. Bud's has them in stock for $1,392
HERE. CMI 20rd mags are good products as they make the GI mags for the Gov't and you can get those for $25ea
HERE. Get him a cotton, 1¼" wide M14 GI sling (we didn't have any leather slings back then) at some place like
Brownell's or
MidwayUSA.
Also, Springfield ships all their M1As with 'NM' front sights and 'NM' capable rear sight bases so he can add a NM hooded rear aperture from Brownells or MidwayUSA and have a nice rifle that shoots better than his did in the Army; mine does.
ETA: Don't bother with a wood handguard, the Army never issued M14s with them as they originally tested them with wood but found out that it got scorched quickly so they redesigned it to a fiberglass unit. The fiberglass one Springfield uses is the one your dad had on his M14.