I just put a 350 engine with a turbo 350 trans into my 73 C30 last weekend. I opted for the energy suspension poly urethane engine mounts. It took forever and that is with the radiator mount, grill and fenders off - so easy access to everything. It was a 4 person job - 1 on the engine hoist, 2 people with pry bars on the engine mounts and 1 person jacking up the transmission. Those engine mounts have 2 metal flat bars that stick out that make it very hard to line up both sides. You have to get it just right as you lower it, like within 1/8". Maybe we were doing something wrong but I managed to the the same engine and trans combo into my 78 5 or 6 years ago with the front clip on and the transmission cross bar still in. I think it was the engine mounts that made it hard to do.
You can see the tabs in the pic.
There are 2 sets of holes on the brackets that my engine mounts go on, I used the upper holes. The engine mounts only fit one way. But with the stock engine mounts it probably would have been pretty straightforward to get the engine in, the metal bar on the top of the energy suspension brackets caused all the issues. We finally got it in when 2 buddies came by and two of us had pry bars to position the engine while the third lowered it and my kid slowly jacked up the transmission.
After that I had to deal with the transmission cross member. I had 3 different ones. The one in there did not line up and I ended up buying one of the tubular ones from summit. Then I tried to torque down the bolts that go into the transmission case and they would tighten up to a point then release. As far as I can tell, the bolts are not standard, they are metric 10mmx1.5 bolts - which almost accepts 3/8" coarse bolts. Maybe it was something else but it looks like someone put metric bolts on this and also chose a thread size that makes you think it's standard. In the end I ran a 10mmx1.5 tap to clean up the thread that may have been damaged when I tried to tighten the 3/8 bolts. Then the 10mmx1.5 worked fine.
