The upper control arms are asymmetrical(the ball joint is not centered), and therefore different from left to right. By swapping them side to side, it puts the upper ball joint quite a bit behind the lower one. This gives you a whole bunch more caster(top of the tire leans back) so the car will be more stable at speed. Most purpose- built drag car front suspension kits have 10 degrees or so of caster designed into them.
77 Vega Estate wagon- project(someday)will have TPI305/T-5, S-10 spindles/axles
72 Vega HB Drag Car -383/'Glide/9"(firstname.lastname@example.org)(email@example.com 1/8th)
76 Vega GT- 400/4spd/9" retired from active duty(rusty)
03 Silverado 2WD ex.cab (work truck/parts hauler)
04 Silverado 2WD ex.cab (retired)
06 Haulin' 20ft enclosed car transporter
93 Suburban- 350/4L60(retired)
00 Saturn SW2- wife's car
01 Saturn SC2- younger son's project
00 Saturn SL2- daughter's car
00 Saturn SL1- older son's ride
98 Saturn SW2- spare
and 3 more Saturn "parts cars"
Note- the very act of listing all of these has made me realize I have some kind of problem.....