These are the going rates for some of the non-E body Hemis:
'69 Hemi Coronet R/T - $123,500
'67 Hemi Coronet Survivor appraised @ $75,000
'70 Hemi Superbird - $250,000+
'68 Hemi Roadrunner - $120,000
'64 Hemi Belvedere - $100,000
'67 Hemi Satellite Conv. - $70,000
'66 Hemi Satellite - $80,000
'70 Hemi roadrunner - $143,000
'69 Hemi Roadrunner - $130,000
'66 Hemi Satellite - $95,000
'71 Hemi Roadrunner (clone) - $70,000
Most of these sold in the $4-5K range new. There's no crystal ball to know what will be collectable in the future but these trucks have a lot of the features that make vehicles collectable, IMO.
That said, as long as you're making the payments do what makes you happy. I like ghost flames. I'm modifying mine but because I'm in the car restoration and restification business and spend a lot of time looking for and fixing original parts, I'm keeping all the stock SRT parts I take off.