1947 Silverside
It started when R. W.  called us and asked if we could put
an Allison automatic into his 1947 GM Silverside coach.
To make a conversion taking the standard transmission off his engine and installing a
V730 would've been quite a difficult job due to bell housing change, cradle change
and overall space problems.  So our suggestion was to remove the
engine/transmission package altogether and go to a late model engine/transmission
package.
R.W. found a 50 Series Detroit with an Allison transmission package which came out
of a 93 RTS coach.  It had the engine cradle and most other parts with it.
We told R.W. to bring the engine/transmission package and his
coach and we were confident we could make the installation for him.
After seeing the coach I was surprised to find out the engine
compartment had less space than I remembered to be from 15
years before when we had a coach like that in our shop.
We removed his engine/transmission package and made
modifications to the engine cradle from the RTS and rolled it into
the rear of the coach to find out what various modifications had to
be made to make it work.
We found that the tailshaft and rear of the transmission had to
reach further into the coach to not alter the rear of the coach.  
Also we had to consider the rear spring hanger, passenger's side.
 We removed a portion of the bulkhead, built a new structure to
support the rear spring hanger and give strength to the bulkhead.
At this point we rolled the engine/transmission package into
place for the fifth time and were generally happy with the
engine/transmission  location in the coach.
We made up mounts to the engine cradle to be fastened to
the coach bulkhead and support struts to hang the cradle at
the rear of the coach.  To be able to use the existing radiator
we had to offset the fan and fan drive.  We had to also make a
cavity above the engine to provide room for the head and
valve cover.
Having the engine basically in place we found the driveshaft
angle did not suit and also due to additional horsepower the
rear axle no longer suited.  We replaced the rear axle with an
RTS rear axle that was matched to the engine/transmission.  
After installing the spring pads, rebuilding the brake and
brake chamber, installing the parking brake safety chambers,
we were over that hurdle.
At this point we were left with plumbing up the engine to the
coach (water piping, fuel tubing, air plumbing etc.).  We also
had to install an air surge cooler and make custom plumbing
for it.
The job was finished and the heavier  engine/transmission package
made the rear of the coach lower by approximately 2 1/2" to 3" so it
was decided to install an air bag system to carry some of the load.
Driving the coach now  is a real pleasure - no more shifting, the ride
seemed to improve and the retarder on the transmission is working
super.
P.S.  This job had to be one of the most complicated jobs we have
done so far.  It was an interesting project but not easy.  Don't know if
I ever want to do it again, but at this point there is no challenge too
big.