what damper should I buy

Economical.....Pioneer. I would expect them to be OK for street/strip; we are using one on our 340 that should rev to about 6k and IMHO should hold together (still breaking in slowly). They have a couple of different 360 models depending on year and if Magnum or LA.

Professional Products has an SFI damper for the 360 at a reasonable price; the price on those looks quite variable so shop around.