Need advice on converting D20 Modern to DnD

[Angel Tarragon]

There are some D20 Modern critters that I'd like to port over to my homebrew, but I'm not sure how to approach this. Could someone please give me some advice?

 

[Mithral Silverwave]

Hm... The main thing I think you want to keep in mind is that d20 Modern is generally a much lower-magic game than D&D, so unless you're running a game with very little magic you might want to consider lowering the CRs. Defense becomes AC, but they're calculated the same way, so I don't think you need to change the number itself.