I just finished the vortec head, ramjet cam swap on my 1995 G30 TBI van in December. It made a huge difference when tuned with tunerpro. Only the heads (****** Jegs vortec heads, long story), the GMPP tbi manifold, a $40 Facebook buy with a hole in the side, and the small 196 degree ramjet cam and lifter conversion was done. The van had 106,000 but the short block was original 1995.
There are some differences in the way the runs were made on the dyno. At first I used the tacho adapter, but its made for a square wave signal and was not reliable in this application. Also when the converter would lock, that's why the three readings of the same rpm on the original pull. I think the end results are pretty good for a tow rig still strangled by stock exhaust manifolds and the tiny stock tbi. Exhaust is a custom 409 SS system I welded up with a big quiet 3" muffler and full tailpipe. No headers or oversize TB, both would have made more peak power, but I really was after grunt and mileage at 2000 to about 4000 to tow my dyno. The engine would pull very well on the hills after the work, it was the sucky 4l60e ratios that would be the downfall. 1-3 are way too far apart. I just rebuilt the trans so I sold the van and moved to the 1996 L29 4l80e C2500 I have now a few weeks ago. The vortec style head, bowl ported and the roller cam conversion gained a lot of torque everywhere for towing, even down low. The last runs where made with the tune locked in 3rd gear, locked converter and I used the roller tacho that ended up being about a 150 rpm off and off on MPH, so its not an apples to apples comparison, but its close! With the locked gear and converter, I can use the dyno brake to start the run much earlier to see if I lost any low end. It gained everywhere. Still not a hot rod, but very noticeable when the van and cargo trailer were close to 10000 lbs when driven across the scales.
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The 1994-95 $0D TBI computer works well with this combo when tuned. You would loose out on most if using the stock chip though and run dangerously lean in places. Totally different fuel curve than stock. The older pcm work but are not as advanced or as fast, it is a huge difference in computing speed. I think they have more problems just because they are so slow to react to changes. The swap to the better computer is very easy. You can get them on ebay for $20 or less and some shipping.
