I got an 87 bronco 2 it has the 2.9 in it it's bogging down and killing itself when I get to operating temp either need help on what to do with it or can I swap my 4.9 straight 6 out of my 89 150 to the bronco

 

You need to figure out whats wrong with the 2.9 b4 you do anything else.

You should take about 20 minutes to do these 3 simple tests:
1 Check for any trouble codes

2 Check fuel pressure

3. Test with a vacuum gauge. Most important test with the vacuum gauge is to see if theres a clogged exhaust.

This might be as simple as a CTS/coolant temp sensor reading cold all the time.

 

the 4.9 would be a very hard conversion because of length and weight..

302 yes with fabrication knowledge.. 4.0 v6 yes with appropriate parts

4.9..major mods ..firewall cutting into passenger cabin..not feasible

 

2X

Few years back, I did the measurements to stuff a 4.9L into my B2, you are going to have to cut firewall and move it back almost to the seats! Then have to make a dog house cover like the vans do. Also you have to redesign the dash to allow the engine dog house to fit.

Then you have to figure out how to clear the steering box with the AC compressor(EFI engines). There was another big snag which I forgotten that stopped me from doing the swap.

IT can be done, but its ALOT of mods to do!