try the following

sealants are a waste of time and have a nasty habbit of ending up in your oil pickup

buy the one piece rubber gasket from the efi motors
get some m6 grub screws about 12mm long(uses allen keys which are required to remove them) , about 8 off
clean the sump mating faces properly
tap out the sump mating face ensuring the metal is bent back into shape
apply a thin layer of grease
install 8 off grub screws , remove as required when putting in bolts
install gasket to the block
install sump
tighten in alternating patterns until the gasket just starts pushing out(do not overtighten as the gasket simply breaks)
it is easier to use a small socket (1/8") set with a nuckle at the end for the two bolts at gearbox end
refill with oil , check for leaks and nip as required

big note: clean out the threads on your block before putting in the bolts , do not force them in , if they do not go in easily , back off and try again
if the bolts look suspect , discard

you do not want to remove a bolt from underneath , it must be the worst job on a cvh

be careful when pushing the sump up , do not dislodge the ends , especially the gearbox end you cant see

hope this helps