timing issues on 72 chevy with 250

[hobos72]

i sont know what has happened to my truck but when i got it it wouldnt go over 50 i was told i needed a carb so i bought one had it put on reason for not doin it myself was oreileys sent wrong carb and i didnt know it so it wasnt runnin right so i put new plugs,wires,cap,button,points,condensor still not right so took to shop.guy puts new carb on i get it back and its running way high plus its getting crappy gas milage and the tickin (now i know that all sixes have a tick)but this is outragous wasnt doin it that bad before so is it possible that the timing is set too high and if so how can i adjust it without a light.ive read some people sayn 2 degrees low or high how do i know how many degrees i turn it.