there was a guy on here in PA who did a ZHP engine swap into a 325ixT - it still had the 5-speed manual, though. it can definitely be done, as the oil pans are interchangeable.
i think the best plan would be to find a clean, late-model 325ixT (2004/2005 is ideal as they should be MS45.1 - my 2005 325iT was and it made my swap basically plug-n-play aside from reflashing the DME; no wiring changes), and find a wrecked ZHP donor car (the red one someone posted on here the other day would be ideal for that purpose), and swap in everything that you can (seats, trim, door panels, steering wheel, cluster, front bumper, side skirts, etc etc etc).
it can definitely be done and they make fabulous daily drivers - a decent amount of power, good fuel economy, good handling, loads of utility. and they look OK too.
peter
2004 330i ZHP
2005 330iT ZHP
2010 328iT M Sport