Army pay in 1968 for an E3 was $137.00 to $192.00 with $65.00 combat pay. Almost $1400.00 a month in todays money.
According to the Pentagon, today, an E-3's pay ranges from $1885.80/mo to $2125.80, depending on years of service.
http://myarmybenefits.us.army.mil/Home/Benefit_Library/Federal_Benefits_Page/Basic_Pay.html?serv=147
On the other hand, an O-10 (four-star) gets $15,583.20, more than a congresscritter. Income inequality!