3M sells a spray adhesive - use the high temperature version, pricey but good.

I would recommend you do your best to get ALL traces of the original foam and glue off before you start glueing the new one on. Spread an old sheet over the engine compartment before you start the job, use a glue remover and thank me 5 years down the road when your hood pad is still in place, or save half an hour today and spend another 2 hours re-doing the job next year!!!

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1939 170 - till I was 3, still turns heads
1989 300TE - daily driver has 263k
1987 300E - purrs happily with 120k
1983 300SD - keeps my friend happy