As far as I know this wont work. The 1Gs use 3 motor mounts on the block, while the 2Gs use three motor mounts on the tranny. So my question would be, does the 2g block have the proper mounting points for the front and rear 1G mounts? If it does you might be able to make this work.
You do want to swap the sensors over, the 1g and 2g ECUs are different. The only two I can think of off hand that HAVE to be changed are the MAS, and the Knock Sensor. The ECU is setup specifically for the way those sensors work. I believe the temp and pressure senders are the same, but you still have to swap some so the connectors still fit.
I would look at the 1g in a 2g swap list at
www.magnusracing.com and
www.roadraceengineering.com to see if you can reverse engineer that info and see if there are going to be any other showstoppers.