Starting to Learn on 95 G30 5.7 for Towing

[donf]

For heavy towing I would stay away from a 4l60, 65, 700r4, ect. Unless very light loads. You may not notice it, but there are much larger gear gaps in that transmission family than the 4l80e. 1st is way too low for anything with a little power, 2nd is lower than the 4l80, so you get into a spot where 3rd is too high and 2nd is putting you above where you want to be rpm wise. The only fix is slow down and putt up the hill in 2nd. Not really ideal. If you never tow heavy or never have hills you may not notice.

[donf]

My dyno ate its hard drive a few weeks ago. Today it got fixed and newer software....$890 dollars later. I got a little nostalgic looking at all the old graphs. The old tbi with vortec heads and the ram jet cam did pretty well for a light tow rig, it was the 4l60e with mile wide ratios that finally made me move on. This is a graph comparing the last pull I did of the tbi 350 with a burned chip to first pull of my bone stock untouched tune 1996 l29 454 c2500. L29 is in red. I dont have the 96 l29 anymore either. Still fun to look at comparisons. Comparisons on the same dyno are much more meaningful than having a keyboard warrior punch out that they made 3000 bazillion hp on their tbi. Calibrations are very easy to change and it offsets the curve from there.
l29vs-tbi-g30.jpg

[Fast355]

My dyno ate its hard drive a few weeks ago. Today it got fixed and newer software....$890 dollars later. I got a little nostalgic looking at all the old graphs. The old tbi with vortec heads and the ram jet cam did pretty well for a light tow rig, it was the 4l60e with mile wide ratios that finally made me move on. This is a graph comparing the last pull I did of the tbi 350 with a burned chip to first pull of my bone stock untouched tune 1996 l29 454 c2500. L29 is in red. I dont have the 96 l29 anymore either. Still fun to look at comparisons. Comparisons on the same dyno are much more meaningful than having a keyboard warrior punch out that they made 3000 bazillion hp on their tbi. Calibrations are very easy to change and it offsets the curve from there.
l29vs-tbi-g30.jpg

Your van seemed low on power, but it is what it is and you had manifolds on it not tri-y headers. I tend to believe what the dyno read with the 357 rwhp TBI because I did end up running a 13.9 @ 101 mph in a 5,300 lbs brick like G20 with 3.08 gears and a 4L60E. My 60' was only a 2.2 on that pass as well.

I absolutely believe a lightly moded 350 can make more power and torque than a L29 454 on stock tune. Especially given your van had a 4L60E and 9.5 SF rear rather than a 4L80E and 10.5 FF rear. The HD driveline will eat a bit more power. My 97 L31 Express van with a 4L85E and 9.5 SF swapped into it, with a 395 cam and tri-ys, made 229 hp and 304 tq with valve float killing the power at 4,500 rpm. I put beehives on it and no other changes and it made 257 hp and 310 tq at the tires. Tuned for E85 it made 272 hp and 330 tq. My stock 8,600+ GVW long block 350 TBI in the 83 G20 made 204 hp and 300 tq negating the converter spike. It had 1.6 full rollers, Z/28 springs, thorley tri-ys, dual 2.5" factory catless exhaust tubing upgraded to magnaflow mufflers with a X-pipe added under the driver seat, and a 3704 intake bored to 2" with a 454 TBI throttle body and air cleaner with the matching intake duct. I put a stock 96 LT4 cam in that engine and it made 250 hp and 300 tq at the tires. All 3 were on the same dyno. I also ran my 2011 M56S on the same dyno, totally stock and it was within a few hp and tq of what Edmunds dyno'd another example at that had 70,000 less miles. My M56S made 378 hp and 390 tq. Edmunds recorded 380 hp and 377 tq from the same model on the same model Dynojet 248 dyno.