What race/class combination from Wizardry 7 lets you change the imported characters class in Wizardry 8 to gadgeteer as soon as possible? The best I can find is Felpurr Rogue, but it takes until level 4 to be able to change to gadgeteer.

I'm not 100% sure how importing works, but if it imports the characters using the same baseline stats as ones created in Wizardry 8 then the Ranger is probably your best bet, since it meets all of the gadgeteer's minimum requirements except for Dexterity, and it's only 5 short there, so any race with at least 15 bonus points left over as a ranger should work.

This might be a case where deleting the previous character and creating a new one (the gadgeteer) in its place is the better option though.

This would be my vote as well.