Hey I am in the middle of swapping my stock v6 to a 5.0 307 out of a 69 Chevelle. I know this is not the most powerful thing I could put in there but the pricing was right and its pretty original so what the hell.

One problem I ran into at the moment is that the drive shaft isn't going to be long enough to fit the th350 that came with the engine.
Does anyone know what length driveshaft I'm going to need ?

 

You'll get better response from a 4th generation website - we are 3rd generation cars here, and we aren't the best resource for you.

But - in our cars, a TH350 swap requires a TH350 with a long tailshaft. Then there's the issue with the torque arm mount, so a new crossmember has to be purchased - you'll have that same issue on a 4th gen.

Aside of all that, none of this will be emissions legal, so you'll have a hard time getting inpsected.

And, like you already stated, the 307 will be a step down from your V6 power and performace wise - the V6 4th gen cars would outrun any stock 3rd gen with the 305, so a 307 is taking a step backwards.

I highly recommend conversing on a 4th gen F-body website for more info.

 

Also, a '69 engine doesn't have hardened exhaust seats, so you'll need a lead additive with every tank of fuel, which will quickly plug up your catalytic converter.
That 307 was rated at 200 gross HP, but the final version, the '73, was net rated. It's 115 HP. Your '96 3.8L was 200 net HP. And those 3.8s can be found used for under $200. So the 307 is false economy. Plus there's no room for your distributor, the LT1s used a front distributor.
You're so screwed, all the way around. Just trying to get a good used set of LT1 mounts, exhaust manifolds and a y-pipe is gonna run you another $200+.
Stop while you're behind, and do it right.

 

Sorry. Mr. time.