Do it ASAP. Coolant doesn't compress like air, and if you draw in too much coolant, you will have bent rods/broken pistons on your hands. I heard of a guy with a Quad-4 Grand Am with a cold air intake that was too low. He went through a deep mud puddle right after getting the engine rebuilt. Cost him a rod that bent and 2 new pistons.
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91 Lumina Z34 5 speed swap (autos in these cars suck behind the DOHC)
92 Lumina Z34 5 speed (91 ZR1 Vette brake swap, sig pic)
95 T-bird 4.6l of pure crap
00 Daewoo Leganza (wifes new car)