i recently purchased a 79 vette, l48..the tach was not working properly as it started at 3000 rpm and moved slightly upon acceleration. i removed the tach and replaced the circuit board at which point it did not move at all..upon inspecting the tach i noticed it had an l82 on the face...can the l48 and l82 interchange?...any ideas?..i was thinking about replacing the whole unit but unsure if i have other issues...thanks