I have a 1979 Chevy K30. I am interested in buying a big block but do not know how to make it fit?

Bolt it in. The tranny will bolt right up, the motor mounts should bolt right up, wiring should be the same. The only thing I am uncertain of is the accesory brackets, You might have to use the brackets and accesories from a 454, (such as power steering pump, alternator, AC). But everything else is straight forward.  

you might need an adda-leaf in the front end to keep it fromm sagging lower than the rear from the extra 300lb sitting up front.   

I dont know the k-30 a 1 ton trk . Doubt  he, will need an extra leaf in the front. Might need to move the motor mounts forward to the next mounting holes due to the length of the big block.  

I was led to believe that a Big-Block would not fit because there was no possible way to custum order it from the factory with one.  

That might be, however the bellhousing bolt pattern on a SB and BB chevy are identical, and if I am not mistaken I also think the use the same Motor mount pads. The wiring interchanges between them also, making it a viable swap. I don't think you will need to move the motor forward, but I am not certain. Another thing you might consider if you swap, would be to replace the rubber mounts with poli ones chances are the first hit on the go pedal will finish the life of the old rubber ones.  

my buddy had a 454 in his 83 k10. dropped right in place of teh factory 305. poly mounts are a must, as well as extra front leaves with a 1/2 or 3/4 ton truck.  

Its a 77 model ,that big block will fit, measure from  the rear engine mounting bolt on the small block against that of the big block . im not positive but i think the engine mount sits futher forward on the big block . But he mounting holes are all ready pre drilled on the frame . I do know that in 77 1 tons came with a big block . Its was called industrial . 454 .  The steal upper reciver on the small block is the same as the big block. But that big block will need a 4 core radiator, nothing less will do  

I agree with the 4 core, and add that an oil cooler helps alot. Use a clutch fan from that of a Big Block caddy to improve heat dispersion also.  

Didnt even think of the fan. Great point!  

When I dropped a BB in my '70 Chevy, it bolted right in.  I did have to replace the engine crossmember with one from a 73-87.  The shape allows pan clearance.  You will need to have the accessory brackets off of a BB, along with a 4 core rad.  Do it, you WON"T regret it.