sqlplus remove \r \n \t from spool
I don't think you're going to be able to do this with a SQL*Plus directive. SQL*Plus is a pretty thin client and isn't designed to touch the data from the result set itself.
If you don't want to use the built-in SQL functions to modify the output then I think you're stuck with post-processing a spooled file.
EDIT by DCookie:Since I missed the OP's original request for a non-TRANSLATE/CHR based solution (I focused on the OP's lament that they were stuck with 8i), in fairness to dpbradley I'm going to withdraw my answer and include it as part of this one, since it was clearly considered. Here's what I wrote:
You might try the TRANSLATE function for your Oracle 8 situation:
SELECT TRANSLATE(L,'A'||CHR(10)||CHR(9)||CHR(13),'A') FROM test;