Lift? Who needs lift? I've got a sawzall. heheh.
Lift is really a matter of personal preference and your willingness, or lack there of, to hack sheet metal.
Although if you do too little lift you may have problems with rubbing on the firewall.
As for gears, I would do 4.56 or 4.88 for a lot of street driving on 40's.
I currently have 37's with about 6" or 7" and a little hacking and 4.88 gears. Nothing's going to change when I get 40's except more hacking. And if the tires rub the firewall, I will move the axle forward an inch and a half.
I can't really tell you what should do since a lot of it is personal preference, I can tell some things you should not do but it does not sound like you were going to do anything bad. Hope I helped a little. Or atleast I hope I did not make it worse. heheh <IMG SRC="smilies/smile.gif" border="0">