Insulating the Perris Pacer 1985
Sure hate to say it now, but from most accounts I've read (and a look at the 3M application chart), 3M77 is not strong enough for this application. 3M90 is the one you want in the 3M line, or use a professional grade automotive headliner adhesive.
Pretty sure if you do some searching you can find specific product recommendations on old threads. Use the "Site Search/Google" option at the bottom of the search menu.