Many aftermarket wheel manufacturers drilled their wheels with a dual bolt pattern (10 holes in the wheel) to accomodate different cars. I'm with Pat, I would not weld up anything on the wheels, just re-drill them to the pattern you need (in between the existing holes). This will make them easier to sell when you decide to move on to something else. Check with machine shops in your area and ask if they have a mill or drill press with an index setup to drill 5 holes at 72 degrees at 2.375" radius from center.

If nobody locally can do it, call these guys. Freight back and forth shouldn't be that costly....
http://www.wheelcollision.com/wccsvcs.html