Thanks for the feedback guys,

"Mechanical Magic" from the Sci-eng group gave me the following from
Machinery's handbook...

Machinery's Handbook 19th calls for a shaft of 1/4-13/32 to be:
"Easy Driving Fit" to be .00028-.00047 interference.
"Close Driving Fit" at .00047-.00083
"Forced Fit" .00083-.00146

I can rig up a small press for this thing but it's still best to have
the easiest press possible.

As far as the bearings at each end, they are just drawn cup needle
rollers with no inner ring. The rollers roll right on the shaft. I
will slide the dowel through the bearing ID and then press or lightly
hammer the pin into the 4140 housing and on through to the other
bearing. I will probably start a pin in at the other end just a little
to align, and then the pin I'm driving in will push the other pin out
when it gets through.

Thanks again,
John