If the new beams (the replacement beams) will be exposed as part of the building's "renovated charm" than consider riveting the connections rather than the cheaper welding.
If riveting is too expensive, bolt the connections, but use "square head" bolts and nuts and tie the steel together with "angle iron" connections: they will look "old-timy" enough to keep the "feel" of the original exposed steel.
Black paint of course.