I've never had oil/coolant mixing when I have had bad HGs in my '85. Has always been exhaust gas pushing into the cooling system, over pressuring it and blowing the coolant out the overflow. A pressure test will show the pressure rising with the engine revs, or a chemical test can be used:
- http://arrowheadradiator.com/head_gasket_or_combustion_leak_test.htm

Easy enough to change the HG w/ engine in place:
http://www.4crawler.com/4x4/CheapTricks/EngineMods/index.shtml#CylinderHead

r.c.brown@ieee.org
TruckEditor@tlca.org
Project: 4Crawler
4Crawler OffRoad - 4x4Wire discount code