i know you and jon are working out the adapter bit, but came across this today and thought you might be interested. its a 4 bolt t3 to 3" v-band adapter. wasnt sure if this is what you were going for or a completely diff approach. if you did decide to go the ext gate route this would make things easier. just thought id post it up.
http://www.boostlogic.com/parts/240sx/info_240sx_T3toVbandAdaptor.htm
http://www.boostlogic.com/parts/240sx/info_240sx_T3toVbandAdaptor.htm