It has been a while since I sold the same complete package that you have on offer as it is not a straight forward swop dropping the HR into a DE as you also require to swop out the radiator, condenser, front carbon composite front panel, hoses, and coolant tanks, air boxes etc. etc.
You also have to fabricate some loom work.
The last 2 HRs that I have dismantled I sold all the parts separately, bare block, engine ancillaries, gearbox, clutch, fly, loom, fuse boxes, keys, barrel, and ECU etc.
Unless you find some one that requires the complete package, then unfortunately I think that you may struggle to find a buyer.
Selling separately will take time, however I feel that is the only way to achieve the residuals that you are hoping for.
Good luck.
Alex.