454 engine life questioin

[iluvmy72]

OK.......I posted this question in the 1988-99 board but they still give no response....so I'm trusting my old pals here at the 67-72 site for info or help or whatever it is I'm asking.....
OK.....I'm a new burb owner....okok I bought it used but it's still my first burb.....it's a 94 2500....clean vehicle.....no leaks....oil change every 1,500 miles(bought from a friend and insists on it being changed every 1,500 miles and with valvoline synthetic nontheless)......and power flush done with the transmission system every 50 thousand miles.....all miles are highway with not much mountains or hills(he's that boring considering it's a 4X4 and he lives in Utah).....the 4X4 was just a image thing for him.....he even washed the under side everyday during winter to get the salt off from the road......LOL....anyway with all that being said, how long would I expect the engine to go if it has 135,000 miles on it? It's a 7.4 Liter 454. Someone told me it should go at least 250,000 miles before it even begines to get tired if it's kept in good condition. If that's the case, then I'm stoked!!!.....I only paid $3,800 for it. Only 3 things seem to be wrong with it and they are not engine or drive train issues. One is the brake light is still lit even though I released the ebrake, dome lights dont come on when the door is opened.....the indicatoer linkage is not working but I know which gear I'm shifted into anyway. But that's it. I will be using this beast in 3 months to bring back my 72 GMC from Cali......So I want to get it in shape for that. Should I do the K&N filter thing as well as Lucas for the trans mission and engine? Any advice for a high milage engine like this is usefull to me. Thanks.