Going for something like 45mm, using spacers to take up any extra, will mean you can get virtually any replacement headset on there in future. Many 1990s road bikes had the steerers cut right down for 33mm stack height Shimano 105/600 headsets. They were crap headsets* which didn't last long, and replacements are both difficult to find and expensive.
*there was a quiet revolution in headset design around 1995 when people started using loose races or cartridges that could move relative to the pressed-in cups; this pretty much eliminated the "indexed steering" problem that used to kill headsets. It took about 150 years to work this out.
Going for something like 45mm, using spacers to take up any extra, will mean you can get virtually any replacement headset on there in future. Many 1990s road bikes had the steerers cut right down for 33mm stack height Shimano 105/600 headsets. They were crap headsets* which didn't last long, and replacements are both difficult to find and expensive.
*there was a quiet revolution in headset design around 1995 when people started using loose races or cartridges that could move relative to the pressed-in cups; this pretty much eliminated the "indexed steering" problem that used to kill headsets. It took about 150 years to work this out.