I loved these pajero evos
Remember only 2500 were made and all the parts for the vehicle were specific, as in they didnt reuse parts from other mistubishi models. So prepare to face some issues. Information is also limited as they werent enough of them to have active forums with detailed information.
As regards the tappets, i would have thought they would use hydraulic lifters.
Can you post some pics of the van and build?
Many moons ago i had the opportunity to check out this 1 when it was for sale and i was very impressed.