Welcome!
The B74.1 series of cars are on sale because AE is trying to get rid of them as they released the B74.2 series of kits last year and they want people to buy the newer kits instead of the old.
I have the B74.1D which I race on mixed indoor carpet, and indoor clay. Most of the time, its on the indoor carpet. I am running 4wd 13.5 stock class. So far, I had been using stock setup which is not ideal for indoor carpet as it is more for clay/dirt as I got the dirt version. I switched to the red springs which are kit setup in the carpet version of the .1, I also changed out the center diff oil to 500K which made the car even better. The local guys are running 1-2 million in their center diffs, around 30k in the rear, 10-15k out front. I am getting more shock and diff oils soon so hope that I can get the car dialed in. Fact: I got the B74.1d last black friday on sale for 300 which is a steal, it was my birthday present, it was also my first 4wd car, and first race grade kit I built up so I had to get used to some new technology with the car (coming from 2wd bashers)
Now the B6.4 is the most current 2wd buggy from AE. The B74.1 is the older model from AE which came out in late 2020 I believe.
It all depends which class your local track / club races the most, also you have to find out if they are doing spec or mod, or open classes.
2wd buggy stock is 17.5T Brushless motors and the esc in blinky mode (zero timing, no turbo or boost timing, just motor can timing allowed)
4wd buggy stock is 13.5T Brushless motors and the esc in blinky mode (zero timing, no turbo or boost timing, just motor can timing allowed)
Well, atleast those are the rules for my local track/club, others might be different so always check in first.
My track, 2wd buggy is more popular but its mostly a mix. We do have a few stadium trucks and SCTs come out once in a while.
I would also check in with the local racers too see what they are running, what setups and stuff like that, what is best for the track ect.
Next is parts availability if you break something. My local track is just a track, no hobby shop so I keep a bag full of spare parts, but for the last 3 race days (5 track days) I had not broken anything on my 74.1 which is really awesome and amazing.
If your track has a hobby shop, see what parts they carry the most for the brand, and car.
AE is US based so parts are easy to find here in the US. Same with Losi and Tekno. Other brands from around the world like Yokomo, Schumacher, Xray, those parts might be harder to find, and more expensive. (Atleast here in the US, not sure where you are located.)
Also to mention, AE released the B74.2 series of cars currently, they offer some upgrades and updates from the B74.1. The biggest difference is the ball cups and 13mm bore shocks.
If your interested in the B74.1(/d) check out my build threads.
Build Thread:
https://www.rctalk.com/forum/threads/team-associated-b74-1d-4wd-buggy-build.136702/
Build Thread 2.0 (for setup and races):
https://www.rctalk.com/forum/threads/team-associated-b74-1d-4wd-buggy-build-2-0.136947/
As far as the locals at my track. Most of them for 4wd are running TLR 22X-4s, some are running other brands like Yokomo, and Xray but there are only like 1 or 2 racers with them. For 2wd, most are running the TLR 22 5.0, AE B6.3/.4, and again, some xray's and yokomo's here and there.
IMO, if you go with a 4wd, I would get the dirt version of the car, or which ever one comes with a center diff as many people these days run a center diff on clay and carpet. If you are racing on carpet with a dirt setup, I would immediately get some heavier diff oils like I mentioned, and some heavier shock oil (for the front)
I would also compare the dirt version car to the carpet version car for any other adjustments that are different between the 2. (This is what I did)
If you are racing on indoor clay, the dirt version kit setup should be able to work. Just talk to the locals and see what improvements you can do / change.
For more footage of my B74.1d in action, check out my YT channel:
https://www.youtube.com/@davidbulles5694
Some other racers might be able to chime in and give their thoughts.
@bill_delong @Iowa crawler @Bogda89 @pl9171