I have no experience with the Hyundai engine, but the 3.0L Montero engines all have roller cams..... the early (pre-'89) Caravans did not.

The Hyundai car cams likely have the torque range a little higher on the rpm curve. To find out, check the specs on the Hyundai and see where the torque and HP peaks are and compare that info to the Montero 3.0L engine.

The Diamante heads look like the Montero heads, but have 2cc less volume in the combustion chamber..... which will result in a higher than stock compression ratio. A little higher ratio won't hurt you unless you also have the engine decks and heads machined. Then, it might put you a little higher than you want - but you won't know unless you take measurements and do the math. The Diamante cams are waaaay different than the Montero cams. They'll give you more top end, but the bottom end of the curve will suffer..... particularly with larger tires.

Roller cam Caravan heads are the same as Montero, but you'll probably have to use one longer valve cover bolt on each head. The cam sprockets on these heads are stamped, where the Montero has cast sprockets - not a show stopper.

There are lots of things to consider when changing to another engine and AFAIK, Dave is the only forum member who has compared the Hyundai engine to the Montero 3.0L.

Frank