I would say generally Atlas makes pretty good locos.
One of the problem is buying stuff off e-bay and not knowing what you are getting, specially
The problem is getting parts to repair them. and this goes with most manufactures
except for one, ATHEARN.
I have worked with Athearn for 40 years and am very familiar with their product line
and stock many parts.
The way I have approached re-powering and getting older diesel locos from any manufacture
to work is by putting an Athearn mechanism under the shell.
Over the years I have done this to hundreds of locos and it has worked out very well. This is because
the parts have been available and I can adapt them to just about any application or type of diesel.
I have also been able to adapt older Athearn parts to work with upgrade parts that Athearn has changed
over the years, example is underframes and trucks.
The other big question is how much time and money do you want to put into the project. This is one of the critical questions you have to ask yourself.
Might not be a bad Idea to check with the manufacture, if they are still in business, of the availability
of parts for the loco you will be buying.