I cannot comment more than SF about the "solid" word...usually surviving to a gambit is done with fearless moves...if an "easy" way exists to play versus it, then the gambit is already of state of being refuted...and it's not the case for the Alekhine/Chatard gambit.
OK, my recorded lines after 1.e4 e6 2.d4 d5 3.Nc3 Nf6 4.Bg5 Be7 (when I play 3...Nf6 I use to play here Bb4, McCutcheon variation) 5.e5 Nfd7 (5...Ne4 and 5...Ng8!? Heidenfeld var. are maybe next thread topics

) 6.h4 (6.Bxe7 Qxe7 is interesting too, but in my opinion Black has easy plan compared to classical Tarrasch Boleslavsky with a couple of bishops more on the board .. and now 7.Qh5 is one system given by Watson, but some work is useful here specialy for Keres recommandation with 7... oo and 7.Qg4 is one idea of english master William Pollock)
And now McDonald adviced to decline the pawn gambit and play 6...c5! one idea being that 7.Nb5 is countered with 7..f6! and here 8.Bd3 a6! because the bishop grab is messy 8...fxg5 9.Qh5+ Kf8 10.Rh3 g6 11.Bxg6 Kg7 12.Bd3 c4 13.Rf3 cxd3 14.Qf7+ Kh6 15.hxg5+ Bxg5 16.Rh3+ Bh4 17.Nf3 Rf8 18.Qxe6+ Nf6 19.Rxh4+ Kg6 20.Qd6 +/=)
The reason for the decline is more because White has strategy with not so much chances to lose this game: 6...Bxg5 7.hxg5 Qxg5 8.Qd3 modern theory move according to Eingorn See Vock-Narciso Dublan,Capelle la Grande 2006 (forum chesspublishing)