I was going to suggest same - since not a big gap and foam is already black. I'll be doing the same to (eventually) re-install heater assembly into Swinger.
Now, curious minds would like to know - - how many rows in your (22") rad - - and, is the core standard orientation or High Density (ie: 30% more tubes in same space) - - and, how many 'vanes' in w.p. - - and, what temp. is t-stat rated - - and what fan setup are you currently using? Remember that the cooling fan has basically little effect above city driving speeds. :???:
