Hi, I see you decided to try and bolt the larger mounting positions towards the rear of the engine from the outside. On mine, I've passed tubes through the sump itself and they bolt from under the main pan.
Who is going to do your welding? Mig or Tig ?
If I can offer any advice, I would suggest you make the whole sump and weld everything apart from the bottom plate to completion, then rework the part that you have made so far so that it sits flat again on the plate. When you come to weld the whole assembly to the plate, use a Mig and weld from the inside. If you weld the outside you will run a huge risk of getting too much heat into the stainless and it will pull and shrink like a bast**d. Run as low amps as possible to do the job and get penetration.
Elliot