IFR DEP HAD CONFLICT WITH 'WARBIRD' ENTERING DOWNWIND.

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ON TKOF FROM RWY 29 AT BED; IFR IN VMC; ASSIGNED HDG 310 TO AVOID SMALL VFR SINGLE TAKING OFF AHEAD OF ME WHICH WAS DEPARTING STRAIGHT OUT. A VFR SINGLE AHEAD OF HIM WAS CLRED TO TURN R TO ENTER R DOWNWIND PATTERN. I HAD BOTH SMAS IN SIGHT; 'SPLITTING' THEM AS I CLBED TO MY ASSIGNED ALT OF 2000 FT (1867 FT AGL). AS I WAS DOING THE POST TKOF CLBOUT CHKLIST; I SPOTTED A LOW WING RADIAL ENG SINGLE (WARBIRD?) HEAD-ON AT A CONVERGING ALT. HE WAS APPARENTLY SOMEWHAT OVERSHOOTING AN ENTRY TO THE R DOWNWIND PATTERN (PUBLISHED PATTERN ALT IS 1933 FT); TO FOLLOW THE SMA THAT HAD DEPARTED 2 AHEAD OF ME. I HAD TO DIVE SOMEWHAT AND ALTER COURSE CLOSER TO THE 'STRAIGHT OUT' SMA. TWR HAD NOT ADVISED ME OF THE CONFLICTING TFC. I BELIEVE THE LOW WING SINGLE OVERSHOT HIS ENTRY; POSSIBLY DISTR BY TRYING TO MAKE PROPER SEQUENCING ON THE SMA TURNING DOWNWIND. MORE IMPORTANT; THE TWR CTLR SHOULDN'T HAVE THOUGHT THAT HE COULD BOTH HAVE A LONG LINE OF VFR TFC ON A 1933 FT R DOWNWIND; AND HAVE ME DO A R DEP WITH A CLB TO 2000 FT. ONE ADDITIONAL UNUSUAL OPERATING FACTOR AT BED SOMEWHAT INCREASED THE CHANCE FOR A CONFLICT. AS AN IFR; I WAS TOLD TO KEEP ON GND FREQ UNTIL I HAD COMPLETED ALL MY PRETKOF CHKS. WHEN I RPTED READY TO GO; I WAS SWITCHED TO TWR AND ALMOST IMMEDIATELY GIVEN TKOF CLRNC. THIS KEPT ME FROM HAVING THE USUAL OPPORTUNITY TO LISTEN IN TO TWR DURING THE MIN OR SO OF FINAL CHKS TO GET THE IDEA OF WHO'S COMING AND GOING. THAT WOULD PROBABLY HAVE GIVEN ME THE OPPORTUNITY TO ANTICIPATE THE ARR OF THE LOW WING SINGLE.