I am currently building an 85 W350. It has a tired 360 with a decent shifting 727 with 4.11 gears. I have the option of buying a low mile 400/727 for cheap. Would it be worth swapping transmission tail shafts to bolt up to the np205? Or should I just freshen up the 360? I do have a good set of 73 340 heads for the 360. I intend to use the truck to pull a 25' gooseneck trailer for hauling cars, trucks, and building materials. I will probably never take it more than a couple hundred miles. I know it will be easier to get power out of the big block but I don't know how much it will cost to have a transmission shop swap tail shafts. I know it's pointless to worry about mileage with this rig but many argue that the big block will be about the same as a small block. Opinions?

Stroke the 360.

I should add that it is somewhat of a budget build.

Nothing to gain with the later 340 heads - 587 J head 1.88 intake probably same or similar to whats on the 360 already(unless they are already built, of course..). Provided you get everything truck specific for the 400 - pan, motor mounts, radiator, etc. I'd do the 400. Otherwise stick with the 360. A lot depends on what the 400 is coming out and can donate to the swap. I've done a few 727's and could probably tackle the tail swap with a good service manual. Best to ask questions on that swap for whatever small differences might exist year to year in the transmissions. If you're paying someone make sure to ask those kind of questions to see if they are on their game.

If you can swing it, stroking the 360 would probably be the best option. There would be little you would have to change in the rest of the truck to use a stroked 360.

The 400 is a good motor for towing, but in addition to buying the 400 there are additional expenses that would be a draw against the price of the stroked 360, and the stroked 360 will be more CI. To change the output shaft so the big block 727 will bolt up to the transfer case, everything needs to come out of the case, you might as well have it refreshed while they are changing the output shaft, more $$$. If the 400 is not a truck motor, you get to buy the truck oil pan and pickup tube, and truck exhaust manifolds/headers, and you may have to deal with a different rad (the bottom hose may be on the wrong side of the rad). Adding the few inches to the wiring harness isn't expensive, but another thing that will need to be done.

Add up your total costs for both options, and go with the most CI for the least money. If both are near equal, its hard to beat a fresh motor.

The differences between the 73 340 heads and the 85 360 heads should be slightly larger exhaust valves, and the 73 340 may, or may not have the hardened exhaust seats the 85 360 heads will have. It may be cheaper to add the bigger valves to the 360 heads then to buy the 340 heads. Gene

Unfortunately you can't do much with either of those engines if you're on a tight budget. The 360 isn't going to tow your gooseneck + car all that well but it'll do it if you feed it enough fuel. The 400 would do a little better but a stock, tired smogger 400 isn't a ground pounder either.

A "stokish" 360 vs a "stockish" 400 is a close choice. That said, I would probably put my money on the 360. The 400 with stock stroke is hard to build. The 360 has lots of choices and available parts... including Magnum heads at moderate cost.

If you make that 400 a 451 with 440 stroke crank it would really be worth it. But bigger budget.

Keep the 360 with or without a stroker.

Changing engine families always ends up getting bogged down with issues like the aforementioned transmission compatibility, accessory brackets, insufficient cooling, mounts, oil pans, ecu, throttle linkage, exhaust, and on and on, unless you have a donor of the same or similar model year and configuration.

If it ain't broke, don't fix it.

Your best budget move is to build the 360. Use a set of magnum heads and kb107 pistons to get compression up. It will have no trouble making 400lb ft of torque at a lower rpm friendly to towing. 360 with piston change and magnum heads will be much more efficient than either of the smog 360/400 motors you have now.

Depending on if the 400 is already set up for a truck, nothing beats cubic inches. If you need to pursue any truck specific parts for it or do any rebuilding on it, the benefit to cost ratio drops.

A stock stroke 360 with magnum style heads and good quench with as much compression as you can get away with on local pump gas may be the best budget approach.

IMO a 360 is a bit light on torque to tow with, but with the right gear and being your in Wisconsin, you may be able to live with it.

Even if you just re-ring what you have, the Magnum heads should flow better.

I would go so far as to look into adding a 518/46RH OD trans to tame those 4.11's down for some highway fuel economy.

Kevin

Thanks for all the input guys. I have found a fresh mild 360 that I am going to buy. It has an rv cam, flat top pistons, and j heads with 2.02 valves. It should work for what I want it for. Twostick, I am strongly considering an od trans