take it off, take it to your local welder, give him $20 and say fix this please.. most likely you will be set, do not do not use gaskets, use copper permatex and let it sit overnight,
i suggest getting some grade 8 bolts from the hardware store with lockwashers, replace the ones you can, some i think are used to hold the dipstick.. never looked at the dr side very well. in any case your std grade 8 bolt from a hardware store, something like 60 cents, will hold up to the heat and not loosen if you use the cheapo 5 cent lockwashers.
they are usually zinc plated or something so they look better than the rust of the factory bolts.
if you do this, dont get stainless bolts, i read somewhere stainless expands and contracts more than any other metal.. do you really want bolts that expand and contract?