Hi Miles -- Here's the issue with stock seats. The stock (base) slides are not meant for the kinds of speeds/impacts that may occur during competition. Yes, they pass NHTSA requirements, but in the SCCA, NASA and even Lemons, we've seen stock seats fail -- a lot. As such, during an impact, seats may become dislodged from the slides. If the seat breaks loose and settles (downward) between the slides/guide-rails, the seat-belts become useless... and you're going to get hurt... or worse. Same goes with the recliner mechanism. Best you can do (if you want to keep the stock seat) is to weld the recliner latch closed and pick the best, nominal seat position you can that fits your range of drivers and then weld the seat slides. That said, there are competition-rated seat slides and you should probably look into them.
Here's the way I look at it -- and this goes without any apology for the pontification that it is meant to apply: if you've got a $50 head, get a $50 helmet.
Rationale: if you've got a $50 body, use a $50 seat. Yes, this is Lemons and I've heard (time and time and time again) that Lemons isn't "real" racing. That's bullsh*t. Racing lawnmowers is "real" racing. However, the speed we're going in our little crap-cans is still 20% faster than my fully race-prepared SCCA F-Production Triumph Spitfire went in 1970 when I went through Driver's School. You've probably got $2,500-3,000 in your car (or you will have when you're done). Another $200 for a good seat with competition-rated slides isn't going to break the bank. But without it, you make break something else.
All the best -
John
"Age only matters if you're a cheese." Helen Hayes