I've had so many of those cars I've lost count. The firing order is 18436572. I am positive of that. Good luck, and have fun with that GTS.
A 1968 Plymouth satellite 273 is a classic automobile. Its firing order is 1 5 3 6 2 4.
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I believe 18436572
the firing order is the same as Chevy 350 except opposite rotation instead of clockwise it is counter clockwise
1 - 4 - 3 - 2
if its a six cylinder it will be 153624
1 3 4 2
18436572 it's the same as a Chevrolet
1-4-3-2. All aircooled 4-cyl VW engines used the same firing order
All V8 engines have the same firing order. 1,3,5,7 is the left bank, 2,4,6,8 is the right bank and the distributor rotates clockwise. 1,8,4,3,6,5,7,2
"http://wiki.answers.com/Q/What_is_the_the_firing_order_for_a_1968_Impala_-350_cu-_and_the_direction_of_the_order_on_the_dist"
Firing order is the standard 1-8-4-3-6-5-7-2 for the Buick 350 and the distributor rotates in a clockwise direction.