This is the one I'm buying next Friday. I'm thinking it will look great on the Mastiff. The only thing is these are all for Harley Davidson with a CV carb. you have 2 options to make it work:
1) is a CV to S&S carb adapter and finding or making spacers, the other is drilling the correct hole pattern for the S&S carb and you may still need spacers. Me I bought the adapter going to mount it to the backing plate then drill out my S&S carb bolt holes, flip it over and counter-bore them and then do the same thing with the one I bought for the Bagger.