Try this trick. Add 1 quart of ATF to your crankcase. Start the engine, allow it to warm up, and drive around for an hour or so, but do not let the RPMs exceed 1800 (in other words, don't drive at highway speeds).
Then, drain the crankcase, replace the oil filter, refill the crankcase with fresh oil, and your lifter tap will hopefully be gone.
Automatic Transmission Fluid (ATF) has a high detergent content, and will aid in clearing out sludge and small particulates from oil galleys and lifters.
BTW, is this the carbureted 170-180 HP 305 (5.0) HO mill, as used in some Z/28 Camaros and the Monte Carlo SS from 1983-88? If so, then it is probably not a "soft cam" issue.