You should be good to go! Nice installation.
I typically try for a full penetration weld to ensure the weld is stronger than the base metal but in this case it probably isn't necessary.
My experience with the S10 transmissions is they shift easy, therefore the strain on the parts shouldn't be very high at all.
FWIW: I put a custom shifter in an '85 S-10, basically a Hurst stick on the stock T5, bolted it to the stub coming up out of the trans., and it held up for over 100,000 miles.
