yeah most of the 305's were on the gutless side. I think i only ever had one that seemed to have some power. the 283s &307s had more get up and go then the 305s. Heck many of my bone stock l6s had more get up and go then a 305. I had a 70s camaro that had a 250 and that thing could get off it's own shadow at High noon. Now the 67 chevyII i had with a 230 and 150,000 plus on it would lay out 7ft of rubber bone stock and not think twice about doing it.
The casting numbers on the block come back with a few different possible engines, and I told myself it was the L48 350, but I was humbled by the lack of power and had to reluctantly accept it was the 305 version on the list. When I got it the PO had a lopey cam and had the vacuum advance hooked up wrong, and it seemed to have 40hp. I took off the smogger Carter AFB and installed a quadrajet for '68 350, HEI, set the timing and put the vacuum advance on manifold and it ran better, but still a gutless wonder. Installing an old school 300hp/327 cam in it helped but it's still under powered. My previous '65 C20 had a 283/SM420/4.57 in it when I got it, and I had to wind it up to 4,000 to keep up with traffic. What made it more scary was the truck didn't have a center hump to cover the hole cut in the floor for the sm420. There was just a piece of plywood laying on top of the shift tower of the sm420. You could watch the rear yoke and driveshaft spin as you drove, cooked in the summer and froze in the winter. I later swapped in a 350, and someone found a center hump and gave it to me, and I found a '68 C20 Suburban Dana 60 with the 3.54 gears. That truck was so fun to drive after all of that. It wouldn't tow uphill very well, and pulling long steep highway grades was not its strong suit, but it sure hauled @$$!, and set a few land speed records with that truck. Well, I'd go as fast as the truck would go, and it was easily 120. One morning I was running late for work. It was a 17 mile drive. I looked at the time when I backed out at home, and again when I pulled into the parking spot at work, and it was 8 minutes. I got lucky there weren't any highway patrol on that stretch of road that morning...lol...
