No adapter plate needed. That transmission should bolt right up to the bellhousing with the right clutch disc. I'm not sure if the driveshaft slip yoke on your 58 will mate to the t5... You may have to swap the slip yokes or even have a new shaft built.
BBSD, Will it bolt up without shortening the input shaft?
I'm really only familiar with the S10 swap with a 1963-1972 truck bell housing. For the 1963-72 trucks, the S10 input shaft is about 1/2" too long. I won't go into the details around solving that problem here, but for the 63-72 trucks, some modification is needed.
