Well after doing a bit of research on the internets and forums, I did a bit of thinking and scored a set of T5 seats in very good condition from the Central coast. thyey didn't come with seat bases and I found this the hardest thing to score from a wrecker. I finally scored a pair from a wrecker in Fairfield and then the fabrication started. The seat with seat base is taller than a T4 seat and about 6-8 cm needs to be removed from the base to drop the seat down to to the same height, the seat will not fit onto the T4 base and will be too high in the end.
I sliced the base off at a predetermined height and fixed the rake angle so the seat didn't slope too far fwd, I used wide steel strap mig welded to the base and drilled the mount holes to suit the new base, there is a difference between the plugs for the seatbelt plug so that will need to be corrected in due course.
They are firmer and fit better, mind you anything is a better deal than the old smokey smelling complete with ciggie butt burns tired old seats. Would I do this again, in short no... After reading a bit more across the internets, I would go for seats that are the same height as the old T4 seats and as long as they are flat mounted and use the original bases.

As for the shifter, I was tired of leaning over to shift, I had seen the extenders but didn't like the look of them, I scored a spare shifter from a T4, after extending the shifter in my Hiace I figured that it wouldnt be too hard. So The spare shifter had a machined plate welded to the top of it and a Hurst shifter was bolted to it, a bit better height wise without going over the top, and to reverse it simply bolt in the old shifter, needs the short travel mod done to it though.

cheers

Adrian