I have mounted a 6.0 liter (in a '70 Impala) and the mounts are on the same location on each side of the block. Even a good, 30 year friend can be wrong, sometimes...
Do a google search, plenty of results, such as : http://www.s10v8.com/store/LS1-LSX-Mounts-Headers-for-S10-V8-Conversion
Also, try asking your questions on the LS1Tech forum, they have done everything with these engines!

'57 Chevy Suburban; '70 Chevy Impala.