Bartamos is correct about both cost (although his $9.90 cost is for 25 screws - for comparison 1/4-20 x 1/2 hex head grade 5 steel are ~$10 per 100) and the possibility of threads galling on stainless steel. Stainless steel is really not necessary, although the button head torx screws would look good on fender to bed bolts. There are plated steel button head phillips screws that would look just a good there.
