Yes, there were the ribs, but thas was to add strength with using less aluminum. These bellhousings are actually a quite a bit thicker than factory bellhousings, therefore stronger. They do weight a little more, but that is ok.

I am looking for a factory R154 bellhousing to do my next pattern though.

It is better to make torque at high rpm than at low rpm, because you can take advtage of gearing.
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1994 4runner - SAS, 38 TSL's, Turbo 7MGTE swap, Turbo Tranny
Dual T-case, D44/D60 ront/rear