Timing and Tuning Help Please, Need some help with a new purchase Options

[DanPMan]

Just bought a 1975 914-2.0 that has been converted from fuel injection to single dual barrel carbuerator. I haven't had time or opportunity to purchase any manuals or technical information, so I need some immediate help. I realize that I'll have a hard time smogging this combo in Nevada.
Does anyone have a quick reference or source that can help me time and tune the car? I borrowed a copy of the old "How to Keep Your VW Alive" from the library for some fundamental air-cooled primers.
Vehicle has been sitting for a while, but still runs fairly well, but heavy detonation when secondaries are opened on the carb. Looks like the distributor is mechanical-only advanced. The conversion to a carb was complete from a kit of some sort; all fuel injection components removed. The previous owner(s) had made the conversion, added a roll bar, many 911 suspension pieces, eurpean racing pistons all in preparation for racing the car. (Previous owners were/are Porcshe mechanics....)
Any quick help is appreciated?
(need to know where timing marks are located; any special technique for a mech advance distributor, relative initial timing set...)

[xsboost90]

timing marks are under that round cap in the front center of the shrowd. Run the car at 3500 and set timing to 27 degrees w/ vac advance disconnected-for stock timing. There should be a red mark that you line up when its at 27. Take the trunk off and stand in the trunk, makes things very easy! NOt sure on carbs, sounds to me like its leaning out big time, but could be something else. Run it hard and check the plugs immediatly afterwards, should tell you something. Disconnect the vac advance and drive it, see if the detonation goes away, mine did, i connected it to the front of the advance instead of the rear near the dist. Not sure why but it works better, advances instead of retards i guess.