100fires,
Welcome to Stovebolt.com
I have put a few 261s into 1954 Chevrolet trucks.
The place to start is to ID your engine:
find and post all these codes and we can start directing information/links as appropriate for the year.
The few topics that are dependent upon years are:
- location of water pump
- water pump (cooling system) hose diameters to radiator
- 6v/12v flywheel/starter
- front motor mount location/configuration
- carburetor/PCV/linkage
- oil-gauge sender
There will also be other considerations dependent upon staying 1954 6-volt or converting to 12v.