Well do what you wan't with it. Change the front end and rear end and put in a nice big block or small block if that's what you like. Try and keep it a Dodge if you wan't which would be cool since you don't see that much. But since you got the frame off, worry about one thing at a time like striping all the old greese, oil and paint and repainting it all nice AFTER the front end and rear end is all taken car of and any other frame mods you will do to it.
So I guess you should look into the front end and see what kind you wanna put on there first if that's what you wanna do.
Others here will put their 2 cents worth in as well and will be of better help than me.