Using a Reis tripod
 

I have a very nice Reis wooden tripod with an A250 double tilt head that I would like to use. Instead of a bowl on top of the tripod, it has a metal plate with either a 1/4 or 3/8 inch thread. If I wanted to use a good tripod head on top of this, what options are there for heads that screw in to the mount rself also has a screw-in thread tather than go through a bowl on the top? The tripod ito hold the A250 head. I am looking for a good fluid head which has smooth pans and tilts.

I know that the Manfrotto 501 head has a 3/8" female thread. Probably the same for the 503.

Is this standard for most video tripod heads? How do they attach to the bowl in the video tripod base?