If I am replacing the trans fluid and pan gasket in a 67 Powerglide, how much trans fliud should I add when refilling?

thanks
JL

It can vary a bit. I'd buy at least 4 quarts.
After the filter change add @3 (or slightly less - check the fluid level on Dipstick after the 2nd Quart), start engine and idle to warm, shift selector through all gears ( R,P & L ) then back to Park with your foot on the brake and then recheck fluid level.
If it is slightly below the "Full" line and the trans is still a bit cool I would leave it.
If it is nearer the "Add" mark I would add and additional 1/2qt/Pint and then recheck.
Do Not overfill your trans.

Hope this helps;
John

Acccording to this chart (http://www.tciauto.com/tech_info/fluid_capacity.htm)4 qts. plus whatever the torque converter holds, depending on its size.

Mike