Radios are flashed through the hboot menu. If you go into Settings, then about Phone, what are the Baseband version numbers? You probably already have the best radios for this app if you accepted the most recent OTA. The data drop problem isn't only a problem for the Bolt; it's happening to pretty much everyone on Verizon with 4G. Hopefully they work it out, cause it's very annoying.
Some radios work better with certain ROMs because the developer used that radio set when compiling it. I have tested a ton of ROMs on various radios and can honestly say that I only notice slight differences between them depending on the ROM. For Thundershed, the .19 radios work the best for me; i.e. I get the fastest data speeds and most consistent connection with them.