lenco oil leak oil to use?

I have a new lenco st1200 ,5 speed with manual shifters.
I was told by them to use str.30 conventional oil.
the oil leaked out of drain plugs and reverser and reverser detent area.
still never used,just sitting in garage.
lenco told me to drain and put 60wt. oil in it.
can any of you advise me from your experience on these issues, and other issues that will show up in the future with this?
what fluid lube you think will be best for me?
this is a radical street driven and drag car,1000hp
the trans is really difficult to get in and out so im hoping you can help me find all issues before they pop up one at a time.
thanks for any help and advise.

 

I use only st 30 wt non detergent motor oil. My st 1200 leaked at the reverser detent. It was the allen screw detent. The detent assy. has a plunger and a spring and another small allen inside of it. the oil was seeping around the little allen and down the plunger and out. take it apart and seal the small allen. Seal the large threads on the large allen and leaks stopped. Hope this helps, Tom.