making a notch?

2X3 tubing is good but what thickness. The shop down the street has 1/8", 3/16" and 1/4" thick.

3/16"
The advantage of a multi piece notch is you can weld inside the uprights off the frame for more strength!

Is 1/8" to thin to use when using 2x3 for a notch?? Should 3/16" be the minimum??

Yes 1/8"wall is too thin for any part of a frame member!!

I would have to dissagree. If properly designed you could build an entire chassis out of 1/8" thick materials if you really wanted to.

False...

What's funny, is everyone has told me is has to be at least 3/16", however the stock c-channel portion of the frame is only 1/8". If I were to go with 1/8", I would just make some gussets to be on the safe side.

1/8" tube is plenty strong. Your factory frame is technically thinner. The outer C is .110" thick, and the inner C welded inside is ~.083".

3/16" will work if that's all you have, but I only use .125 wall tube for my notches and back halfs. I am building a full frame for my new project, and the entire thing will be 2x3 .125.

Good info...

i'd say try to match the thickness of the frame - 3/16 seems a bit much for a toyota.