Is there an ideal way to measure the converter and transmission outside the car to make sure you should have the proper clearance between the converter and the flex plate before installation?

Yes, you can use a straight edge, laying it across the face of the bell housing. (Engine side). Then with the converter installed in transmission, take a ruler and measure the distance from the straight edge down to the mounting pad of the converter. The measurement should be as follows:

• GM 4L60 1 1/8" from Bell housing to Pads
• GM 4L60E 1 1/8" from Bell housing to Pads
• GM 4L80E 1 1/8" from Bell housing to Pads
• GM TH 350 1 1/8" from Bell housing to Pads
• GM TH 400 1 3/16" from Bell housing to Pads
• GM Powerglide 1 1/8" from Bell housing to Pads<

Note: Distance may vary either way .050".