Kramer C serial number denotes it's a 1983 model. Kramer was using Poplar, Maple and some Alder in 1982/83. The pickguard models are the least desirable but that early hockey stick neck adds to the value for the right buyer.
If that guitar is super heavy then it's probably Maple, Poplar weighs about what Alder does. I've owned two 83 Pacer Carrerra's that were Maple and they were HEAVY AS FUCK as you say JBT. FWIW Lynch's #1 Tiger is a Maple body. I have a maple bodied JEL guitar I built and I love it.
Pricewise anywhere from $1500-$2000 I'd say because of the hockey stick headstock neck as those were usually only seen on the Barretta's at that time., they must have needed a neck or that's not the original neck. I've only seen beak necks on anything other than Barretta's. Looks like it has a Dimarzio bridge p/u of some kind as well, probably a SD.
Your buddy can research more here.
http://www.vintagekramer.com/