A direct replacement for your Strat hardtail bridge will need to share the same screw hole mounting pattern as the original part. Fender use two versions of this 3-screw pattern for their hardtails; the Vintage .89”/22.6mm and American Standard .827”/21mm spacings (measured between the centres of two adjacent screw holes).
Your choice of replacement/upgrade parts can be limited depending on the version your Strat uses. It isn’t the quantity of options to choose from – there are many brands who manufacturer this type of bridge – rather the variety available.
The narrow American Standard (or “Modern”) version is incredibly well catered for. Many of the available options offer much more than the typical Strat hardtail; Fixed bridges, low-profile designs, 3D saddles, etc.
The Vintage spacing appears, to me anyway, restricted to the “standard” hardtail design. I’m unsure how common the Vintage pattern is but I’d imagine it’s limited to much older instruments and likely any reissues. It would therefore make sense that these replacements are just that, a replacement in keeping with the original spec, rather than an upgrade.
