the ones at the back of the inner may have been glued, and the glue reacting with the different composition of rubber back then may be why they wind up looking tarry from the heat - and the assembly manual shows staples [my 58 didn't have them], but the only place the staples are really needed is the piece across the bottom that covers the gap between the inner and frame, which reduces road spray into the engine compartment ... I've just left those off where they're missing, but some folks manually replace staples, which I wouldn't expect to last long unless you can work out something of stainless .... you could just use sheet rubber for there, or something like truck inner tubes cut to suit, I haven't seen those reproduced
Bill