3.91 or 4.10?

Get rid of the wussy Magnum cam first, or at least retime it. I mean, from the Factory, they were installed on a 119 Installed Centerline for truckes to bleed off cylinder pressure, to prevent detonation under load.
They run a whole bunch stronger at about 107. So by the math, they are 12* retarded!!

Fix the cam timing, it costs you a gasket and I bet it goes 13s even with the 3.23s which, with a 4 speed should get you 98 in Third gear at 5500 .......
Four series gears will force a shift into 4th, and I guarantee you, neither of the two options are gunna be correct.
3.91s will hit 98 at near 4770, and 4.10 at 5000. whereas the factory cam is done around 4500
At 3400 pounds, 98mph is already a 13.9
At 3600 to go 98 requires 278 hp, and that might get you to 13.68, with a SS chassis. With a street chassis you can expect to be about a second slower;
partly from the crappy 60ft, and partly from trapping off the cam.

But yur stock 5.9, even with the cam in correctly, might never make 278 hp, so, at 3600 pounds, she'd never make 98 mph. jus saying.


And honestly, as a city car, yur already making more power than either your tires or the cassis can handle, and 3.23s are already the right gear to downshift back into first, at 35 mph. which should hit 3750 just before tirespin.
3.91s will get you 35=4540, massive tire-smoke, and bam, time to shift into Second, that's gunna suck.