It is possible, but I think it is more trouble than it is worth.
The UIM will bolt up to the L36 LIM, but I am pretty sure you need the Gen V to L67 TB adapter to bolt your TB to the L26 UIM.
The EGR Stove Pipe will need to be cut down about 1/4".
You will want to consider using the runner inserts from the L36 in the L26 UIM, they should fit fine, or the ZZPerformance HV3 inserts.
I think you have to plug 2 ports for the EGR, at least that is what I read a while back.
If it were me I'd just get a new redesigned Dorman UIM, and install the reduced diameter EGR stove pipe, block off the LIM to UIM TB coolant ports if desired, and be done with it.
2006 Pontiac Grand Prix GT with SC
1996 Buick Park Ave NA