Trans to engine braces

I put my transmission on my engine and got it in the car today, but I couldn't find the braces I found one but it must have came off the slant six because it didn't fit at all. Are these needed? I plan to find them and put them in there eventually is it something that needs to be done sooner than later or no big deal?

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never ran them on anything , hemi`s down to sbc--------------