Steve this is something that you cant just up and say i like that one ill take 2 please... lots of things have to be considered and you have to know WHAT to look for..
Saftey
Customer Service
Frame Design:
Is it built right
What material
Plenty of cross bracing
Seat belt tabs/mounting
motor mounting
Does the car appeal to you?
How is the suspension?
How heavy is it?
Mid Engine, Rear Engine?
TONS AND TONS of questions should be asked and things taken into consideration before you even think about purchasing a car.. You should also get as many rides as possible in as many diffrent cars as possible.. Diffrent cars handle diffrent ways.. Have diffrent suspension designs and its not something you just walk into a manufacturers shop and go wow that looks cool ill take it..
DO YOUR HOMEWORK!! There are several forums on the internet that if you take your time and read you will get a good idea who some good manufacturers are.
NOW TO MY SUGGESTIONS:
Desert Dynamics, Proven Safe, Good Ride, Motor options are whatever you want, Price is very economical for a complete turn key car
Drawbacks of the DD car is who assembles it? You need to find a reputable builder to assemble the car for you unless you plan on doing it yourself.
If i had 40k to spend on a sand car.. the DD 2 seat mid engine w/ a turnkey 510hp ls1 w/ mendi 4s would be the way i would go... but thats me..
Again get as many rides as possible.. make a list of cars that you like, if they look good to your eye then write them down and investigate further on each company. Not everyone can go and buy a 90k tatum ( cough 3rotortrav ), we have to seek alternatives and there are tons of them out there... Do your homework and make sure that SAFTEY comes before what looks good.. SAFTEY is key.
My Priorities:
Saftey
Customer Service
Reputable company ( will they still be around in 3 years when you need help )
Suspension
Trans
Motor
Saftey
Asthetics ( how the frame appeals to you )