I have designed many 900 mm or 36" vessels. Too many people in this post making things complicate, and lack of vision for convenience for maintenance purpose in the future.
Here are the thinking process;
1. Ask Process engineer to resize to 36" OD or 38" OD such that standard B16.46 series A or B gasket and body flanges can be used. Why bothering using custom made gasket ? Don't go for special gasket or Appendix 2 to show your talent. Run ID for both cases and present to your process engineer for decision.
2. Check P&ID to see what kind of gasket used in Piping Material Spec. Spiral wound, RTJ or other type, and flange rating ? Use the same type and rating. No need for Kammprofile which we only used for high temperature service or in FCC.
Only open once a year, so buy some spares, it is cheap by using standard gasket and can be sourced quickly without special design.
Always think to make your life easier.