These Super Famicom translations/conversions are very similar to the Mother 2 to Earthbound Conversion. The couple of SFC carts I’ve made or tested have had just one original MASKROM, making replacing with a flashed 29F032 even easier than Mother 2, it’s just a straight forward swap, no altering needed.
I use a desoldering station to suck the solder off of the old MASKROM chip. Some people use desoldering braid/wick, desolder pump, or they cut the legs and heat up and remove the remains etc.
I used uCON64 to check the original ROM file. I downloaded and configured the GUI for uCON64 to make life simpler. You can use it to remove the header, fix the checksum, check to see if it’s byteswapped etc. Here’s the info from the files I used.
Secret of Mana 2 (Seiken Densetsu 3 English Translation, 3 Player Patch)
Secret of Mana Enhanced (from Seiken Densetsu 2 cart)
It was easier/cheaper for me to get a Japanese copy of Seiken Densetsu 2 and make an English Secret of Mana than buy the original English cart. As an added bonus, you can now apply the Enhanced patch to the rom.