1990 Mazda MPV performance upgrade question

1990 Mazda MPV mileage: 210,000. Our MPV has a great body, with no rust and a decent interior. We take a lot of time trying to do good maintenance, but the engine/trans are getting worn; obviously with that many miles why not. We want to keep the van, we really like it, but we've never been really wild about the lack of performance. I would most likely be replacing the engine and transmission with new ones. Is there any performance gains to be made anywhere with this combo? I do not think it has much more than 120 hp maybe 150 torque that just is not much for this vehicle to have safe passing power let alone try to tow anything. Any ideas would be welcome. I would also be curious about what improvements could be made in the braking and suspension departments? I have spoken with another mechanic and I'm looking to get a few more opinions. Thank you for the time.