In my opinion, the easiest thing to do would be to swap your swing-axle chassis for a IRS. If you're looking at replacing the floor pans, you can fix the IRS chassis up (pans, clean/paint) then set the body on it. But if you change chassis you'd have to weld your vin number in under the rear seat.
As for wrench's estamate. I'd say that sounds pretty close. I've done a lot of welding on vws, but I havn't converted a swing-axle to IRS. My Ghia's body is a '64 which originaly came with swing, but when I bought the car, it was sitting on a '74 chassis, IRS.
Another thought, Ghia's and bugs have the same chassis (tunnel). The differance is in the floor pans. If you can find an IRS Ghia chassis. Use that and put new pans in it.
