Trying to decide which rear kit to use under my 37 sedan.

TCI claims theirs lowers the rear by 4" I am a bit skeptical since they mount springs under the frame like Chassis Engineering instead of inside like Weedetr and Posie's

I would like to drop rear as low as possible without C notch or use of large or any lowering blocks.

Anyone with experience of this kit or other's to accomplish this?