The MT random number generator code is probably the way to go to insure cross-platform random numbers. It uses integers for all calculations, and it appears to use accepted techniques for generating "nice" random numbers. It should be easy to compile the C code into a Blitz userlib/module.
Already done... Although very few people seemed to care. I compiled a dll/userlib for blitz+ and blitz3D, and a mod for blitzmax... It's in the "programming" forums of the respective products.
Blitzmax Mod:
http://www.obsidianobelisk.com/software/mersenne.zip
Blitz+ and Blitz3D Userlib:
http://www.obsidianobelisk.com/software/mtuserlib.zip
Commands:
SeedRand(seed%) - seed the random number generator
x% = Rand32() - return the next number in PRNG
x% = RandMax(max%) - return random number from 1 - max
x% = RandRange(lo%, hi%) - return random number from lo - hi