Well looked at pricing for Z and N scale, and various sets at the local hobby shops. Z was looking a bit expensive. But found a nice Bachmann N scale set with oval of snap track, power pack and nice set of cars for really cheap at a local shop. And picked up an extra gondola for passengers.
Have been to a couple of rail parks where they run a mix of miniature freight cars and ride on cars for the public.
So rather then taking a saw to the roofs of the freight cars I will just leave them as part of the consist. The Atlas gondola had regular couplers and Bachmann set ramp style couplers. The Gondola with the set and Atlas gondola are pretty similar. So I peeled the bottom off of each and cut them in half, and swapped half of each base gluing them back on. So the scale couplers are between each gondola and match up and the other end of both gondolas has the different ramp couplers and it all links up well.
Perhaps may add another gondola or 2 but the figures tend to add a bit of weight to the train and do not want to over do it.
Will glue this to a base I can take to train shows to run as an amusement park ride.
The figures I have in O scale seem to fill the seats well so it would be very tight to try to fit 2 people to a seat.
Will have to make a control panel for the engineer.