Crank Thrusting Foreward Issues

I put the trans in twice, with the engine already installed, a way I've never done before. I've always removed/installed an engine with the trans already installed. Guess I'll never do that way again.

I am a welder and I have access to a nice miller gtaw. Any special way to weld it up? What about filler rod material?
I've never had any issues mating the engine to the trans with the trans in the car.....
I have have a one cast crank welded and machined on both thrust surfaces. Held up fine.