Yes, chevy engines mount further forward then Pontiac's.

I modified a th350 x-over for my 700r4.
Set the engine/trans assembly in place and test fit x-over in place.
Then mark where new holes needed to be drilled.
Had to move it back.
And may of reversed it and rewelded the trans mount bracket...
Been 3-4 yrs.

Think 200-4r's mount further forward then 700's.
Can you measure from the front lower case to the center of the mount?
Maybe someone else can measure thier th350 length.