Both should be able to handle 18" radius curves, but will look better on larger curves. Especially the SD45.

Len

Tap drill for a 2-56 screw in plastic is #50. Use a #49 for a self tapping #2 screw.

Len

There's no wiring per se involved. The 'Universal Smoke Unit' sits between the to halves of the split frame and contacts on each side of the smoke unit get power from each side. And exploded diagram of the same loco with the smoke unit can be found here:

https://www.bachmanntrains.com/home-usa/dwg/dwgs/50701.pdf

You can see how it fits in the more or less square opening at the front of the chassis.

Len

I've used an MRC AA370 Railpower 1370 DC power pack to run a similar locomotive, with 4 cars and a caboose, around a 15 ft x 20 ft elevated display track in a store with no problems. That layout was level and used brass track with feeders from the power pack every 5 ft. Adding elevations would up the power requirements.

Len

These trucks should be adaptable to those cars:
https://www.walthers.com/heavyweight-6-wheel-passenger-trucks-type-2411-1-pair

You may find them available from other on-line retailers at lower prices.

If they are from the 1998 production run, Kadee #5 or #148 couplers should work. If not, use the Kadee #27.

Len

Technically, the site where all that stuff is located is a museum. Unfortunately, it appears to be unfunded and unmanned.

Len

Beware of any train stuff on eBay that contains the words, "rare and hard to fine", "collectable", and worst of all, "vintage". Almost none of it's worth what's being asked.

Len

Are the passenger cars heavyweight or streamline? It makes a difference.

Len

The simplest way to convert the old cars is using the knuckle coupler of your choice, EZ-Mate MkII's are not super expensive, and Kadee #212 Talgo Truck adapters for cars with truck mounted 'horn-hook' style couplers. The hardest part is trimming the swing limiters off the mouth of the talgo truck coupler boxes.

Len

Whoever set the car order with all those light cars in front shares at least some of the blame on this one. Maybe the RR training department needs to set up a layout with a 'S' like the one in the pic to explain why doing that is not a good idea.

Len

There's a prototype out there for almost everything we model.

Len

Should be a straight board swap and add decoder of your choice using this board:
https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=68_184&products_id=7665

You can compare the diagram of the DC version:
https://www.bachmanntrains.com/home-usa/dwg/dwgs/H617X_IS001.pdf

With the DCC version:
https://www.bachmanntrains.com/home-usa/dwg/dwgs/HOEMDGP38-2(DCCEQUIPPED).pdf

To see where the wires get moved to. It doesn't appear you need to do anything special to the motor.

Len

The high wheel 4-4-0's were designed for speed, not pulling power. Generally speaking, you find the prototype pulling 2-4 passenger cars, depending on their size, or 4-6 freight cars and a caboose. The HO model will probably pull more on level track, but it will not look right.

Len

Moving shells from older, custom decorated or hard to find, locos to modern chassis is almost a hobby in itself.

Len

For a holiday, it seems to be a lot going on at almost all of the sites today.

Len