the t28 turbo is a step down dont do it!
i see alot of people running some kind of t3/t4 turbo.
there are alot of different combos.
there are some people running t4 flanges and running bigger turbos with success.
do a search for garrett76zt,zgad,and dont forget timz! hes at over 600hp with his l28. there are more guys out there. also check out the guys running the holset turbos from the dodge pickups. look for names like thumper,big phil and proxlamus.
good luck and have fun!